U.S. patent number 8,477,267 [Application Number 12/939,407] was granted by the patent office on 2013-07-02 for light-condensing film, liquid-crystal panel and backlight as well as manufacturing process for light-condensing film.
This patent grant is currently assigned to Dai Nippon Printing Co., Ltd., Dainippon Ink and Chemicals, Inc., JSR Corporation, Konica Minolta Holdings, Inc., Kuraray Co., Ltd., Sumitomo Bakelite Co., Ltd., Sumitomo Chemical Company Limited, Toppan Printing Co., Ltd.. The grantee listed for this patent is Toshimasa Eguchi, Ichiro Fujieda, Katsuya Fujisawa, Kazuo Genda, Tokuo Ikari, Atsushi Kumano, Yoshiki Matsuoka, Yoshiyuki Ono, Noboru Oshima, Norimasa Sekine, Ken Sumiyoshi, Motoyuki Suzuki, Tatsumi Takahashi, Kazushige Takechi, Akimitsu Tsukuda, Yasuo Tsuruoka, Shigenori Yamaoka, Hisatomo Yonehara. Invention is credited to Toshimasa Eguchi, Ichiro Fujieda, Katsuya Fujisawa, Kazuo Genda, Tokuo Ikari, Atsushi Kumano, Yoshiki Matsuoka, Yoshiyuki Ono, Noboru Oshima, Norimasa Sekine, Ken Sumiyoshi, Motoyuki Suzuki, Tatsumi Takahashi, Kazushige Takechi, Akimitsu Tsukuda, Yasuo Tsuruoka, Shigenori Yamaoka, Hisatomo Yonehara.
United States Patent |
8,477,267 |
Fujisawa , et al. |
July 2, 2013 |
Light-condensing film, liquid-crystal panel and backlight as well
as manufacturing process for light-condensing film
Abstract
A conventional liquid crystal display comprises a number of
components, so that a manufacturing cost cannot be reduced.
Furthermore, a large-area substrate has problems in shipping.
According to this invention, a liquid-crystal panel is prepared by
forming individual optically functional films, a TFT device and a
light-emitting device on a long thin film and then laminating the
film by a transfer process. A base film to be a substrate in a
liquid-crystal panel preferably has a thickness of 10 .mu.m to 200
.mu.m, a curvature radius of 40 mm or less as a measure of
flexibility and a coefficient of thermal expansion of 50
ppm/.degree. C. or less. Furthermore, it more preferably gives a
variation of .+-.5% or less in mechanical and optical properties to
a thermal history at 200.degree. C.
Inventors: |
Fujisawa; Katsuya (Ibaraki,
JP), Ikari; Tokuo (Ibaraki, JP), Genda;
Kazuo (Tokyo, JP), Kumano; Atsushi (Tokyo,
JP), Oshima; Noboru (Tokyo, JP), Matsuoka;
Yoshiki (Ehime, JP), Eguchi; Toshimasa (Tokyo,
JP), Yamaoka; Shigenori (Tokyo, JP), Ono;
Yoshiyuki (Chiba, JP), Yonehara; Hisatomo (Chiba,
JP), Takahashi; Tatsumi (Tokyo, JP),
Suzuki; Motoyuki (Shiga, JP), Tsukuda; Akimitsu
(Shiga, JP), Sekine; Norimasa (Tokyo, JP),
Takechi; Kazushige (Tokyo, JP), Sumiyoshi; Ken
(Tokyo, JP), Fujieda; Ichiro (Tokyo, JP),
Tsuruoka; Yasuo (Ibaraki, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Fujisawa; Katsuya
Ikari; Tokuo
Genda; Kazuo
Kumano; Atsushi
Oshima; Noboru
Matsuoka; Yoshiki
Eguchi; Toshimasa
Yamaoka; Shigenori
Ono; Yoshiyuki
Yonehara; Hisatomo
Takahashi; Tatsumi
Suzuki; Motoyuki
Tsukuda; Akimitsu
Sekine; Norimasa
Takechi; Kazushige
Sumiyoshi; Ken
Fujieda; Ichiro
Tsuruoka; Yasuo |
Ibaraki
Ibaraki
Tokyo
Tokyo
Tokyo
Ehime
Tokyo
Tokyo
Chiba
Chiba
Tokyo
Shiga
Shiga
Tokyo
Tokyo
Tokyo
Tokyo
Ibaraki |
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A |
JP
JP
JP
JP
JP
JP
JP
JP
JP
JP
JP
JP
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
Kuraray Co., Ltd. (Okayama,
JP)
Konica Minolta Holdings, Inc. (Tokyo, JP)
JSR Corporation (Tokyo, JP)
Sumitomo Chemical Company Limited (Tokyo, JP)
Sumitomo Bakelite Co., Ltd. (Tokyo, JP)
Dainippon Ink and Chemicals, Inc. (Tokyo, JP)
Dai Nippon Printing Co., Ltd. (Tokyo, JP)
Toppan Printing Co., Ltd. (Tokyo, JP)
|
Family
ID: |
35784978 |
Appl.
No.: |
12/939,407 |
Filed: |
November 4, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110126975 A1 |
Jun 2, 2011 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10571543 |
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7852435 |
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PCT/JP2004/018250 |
Dec 8, 2004 |
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Foreign Application Priority Data
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Jul 16, 2004 [JP] |
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2004-209783 |
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Current U.S.
Class: |
349/95;
349/112 |
Current CPC
Class: |
G02B
5/0242 (20130101); G02B 5/0268 (20130101); G02F
1/133305 (20130101); G02B 5/0284 (20130101); G02B
5/0221 (20130101); G02B 5/0278 (20130101); B32B
2457/202 (20130101); G02F 1/133607 (20210101); B32B
2457/20 (20130101); Y10T 156/10 (20150115); B32B
2307/40 (20130101) |
Current International
Class: |
G02F
1/1335 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1493891 |
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May 2004 |
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CN |
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54-126559 |
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JP |
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62-150218 |
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Jul 1987 |
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JP |
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63-283934 |
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Nov 1988 |
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JP |
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7-318707 |
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Dec 1995 |
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JP |
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2000-29034 |
|
Jan 2000 |
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JP |
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2000-352608 |
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Dec 2000 |
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JP |
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2001-312913 |
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Nov 2001 |
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JP |
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2002-62524 |
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Feb 2002 |
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JP |
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2002-69210 |
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Mar 2002 |
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JP |
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2002-90919 |
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Mar 2002 |
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JP |
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2002-98957 |
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Apr 2002 |
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JP |
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2002-148607 |
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May 2002 |
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JP |
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2002-358024 |
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Dec 2002 |
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JP |
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2003-66230 |
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Mar 2003 |
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JP |
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2003-232921 |
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Aug 2003 |
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JP |
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2004-110002 |
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Apr 2004 |
|
JP |
|
2004-151592 |
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May 2004 |
|
JP |
|
2005-259672 |
|
Sep 2005 |
|
JP |
|
Other References
International Search Report dated Mar. 22, 2005, from corresponding
International Application No. PCT/JP2004/018250. cited by applicant
.
Japanese Office Action dated Feb. 10, 2006, from corresponding
Japanese Application No. 2004-209783. cited by applicant .
International Preliminary Report on Patentability and Written
Opinion of the International Searching Authority dated Jan. 16,
2007, from corresponding International Application No.
PCT/JP/2004/018250. cited by applicant .
United States Office Action dated Jul. 7, 2009, from corresponding
U.S. Appl. No. 10/571,543. cited by applicant .
United States Office Action dated Feb. 16, 2010, from corresponding
U.S. Appl. No. 10/571,543. cited by applicant .
United States Advisory Action dated Jun. 1, 2010, from
corresponding U.S. Appl. No. 10/571,543. cited by applicant .
Supplementary European Search Report dated Nov. 21, 2012, from
corresponding European Application No. 04 82 2207.9. cited by
applicant.
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Primary Examiner: Chien; Lucy
Attorney, Agent or Firm: Katten Muchin Rosenman LLP
Claims
What is claimed is:
1. A process for manufacturing a light-condensing layered film, the
light-condensing layered film comprising a light-condensing film
and a long light-guiding film, the light-condensing film comprising
an array of light collectors, the array of light collectors
comprising an organic resin, the array of light collectors being
disposed on a long light-diffusing film with a flexibility of 40 mm
or less of a curvature radius and a coefficient of thermal
expansion of 50 ppm/.degree. C. or less; the array of light
collectors comprising a first surface and a second surface opposed
to the first surface, the second surface contacting the long light
diffusing film, the first surface being flat and having a smaller
area than the second surface; wherein the long light-guiding film
is laminated on the surface facing the light diffusing film in the
light collector in the light-condensing film; the process
comprising the steps of: filling a first irregularity in a support
corresponding to a second irregularity for the array of light
collectors with the organic resin to form the second irregularity
made of the organic resin for the array of light collectors;
transferring the second irregularity made of the organic resin from
the support to the long light-diffusing thin film to form the array
of light collectors, the array of light collectors; and laminating
the long light-guiding film on the second surface of the array of
light collectors exposing the second irregularity.
2. The process for manufacturing a light-condensing layered film as
claimed in claim 1, wherein the transferring step comprises curing
the organic resin in the form of the first irregularity under
pressure.
Description
TECHNICAL FIELD
This invention relates to a light-condensing film, a liquid-crystal
panel and a backlight as well as a manufacturing process for a
light-condensing film.
BACKGROUND ART
As an information society has been recently developed, an indoor
stationary type of imaging apparatus has been required to have a
larger display while for a mobile type apparatus, it has become
essential that it can be used in both dark and bright places.
Furthermore, weight reduction has been required for both types. As
a result, a conventional CRT (Cathode Ray Tube) display has been
replaced by a flat display.
Application of information devices have been expanded from indoor
stationary types to mobile types. In contrast to stationary types,
mobile type information devices are used in various situations.
Stationary type devices are required to have a larger display and
exhibit higher brightness and a wide viewing angle. Mobile type
devices are required to exhibit stable visibility in both dark and
bright places and improved impact resistance such as drop-impact
resistance because they are used in a wide variety of
situations.
Known flat displays include a plasma display, a liquid crystal
display and an organic EL display (Organic Light Emitted Display).
A plasma display is not suitable for a mobile device because it
requires a high voltage from its operation principle, while a
liquid crystal display and an organic EL display which can be
operated with low power consumption are suitable for a mobile
device.
A plasma display has been ahead as a large display because of its
higher brightness and wide viewing angle. However, a liquid crystal
display can be reduction in weight and, as a plasma display,
large-sized. Thus, the liquid crystal display has been recently
large-sized as a plasma display.
Meanwhile, in terms of a mobile device, a plasma display is not
suitable for a mobile device because it requires a high voltage
from its principle of operation, while a liquid crystal display and
an organic EL display which can be operated with low power
consumption are suitable for a mobile device.
Although liquid crystal displays prevail at present, it is expected
that organic EL displays will be increased because of their clear
picture.
Organic EL displays and liquid crystal displays are classified into
"active driving types" where each pixel is equipped with an active
device for driving, and "simple matrix types" where a pixel is
driven by two groups of orthogonal electrodes. An active driving
type can drastically reduce a response time in comparison with a
simple matrix type, allowing a number of pixels to be used for
movie displaying. Furthermore, it can more precisely control
image-quality factors such as contrast and gradation, allowing a
movie to be displayed in a quality comparable to a CRT. As a
result, an "active driving type" is now a dominant driving
system.
While a CRT or an organic EL display is a self-luminous type, a
liquid crystal display develops colors using a transmitted or
reflected light. Liquid crystal displays can be classified into
three groups, i.e., transmission, reflection and semi-transmissive
types, in which a pixel electrode transmits, reflects or partially
transmits and partially reflects a light, respectively.
When a device is exclusively for indoor use as a stationary type,
an image is clear in a transmissive liquid crystal display or an
organic EL display. However, image contrast is deteriorated in an
outdoor area which is brighter than emission intensity of natural
light, leading to an obscure image. When a light source is
intensified for preventing contrast deterioration outside, dazzling
occurs in an indoor image and power consumption is increased.
In contrast, a reflective liquid crystal display has an advantage
of higher outdoor visibility because it reflects an outside light
to display an image, but has a drawback that an image is obscure in
a dark place. Although the problem can be improved by incorporating
a front light, a front light has a drawback that it cannot evenly
illuminate the whole display even for a small display as in a
mobile device.
There is a semi-transmissive liquid crystal display as a liquid
crystal display with advantages of the transmission and the
reflective types. A semi-transmissive liquid crystal display
utilizes both backlight and outside light for displaying, by making
a pixel electrode semi-transparence or forming an opening, ensuring
visibility in both outdoor and indoor places. In most of mobile
information terminals, semi-transmissive liquid-crystal panels are
used at present.
However, an image in a semi-transmissive liquid crystal display is
inferior to that in a transmissive liquid crystal display or
organic EL display in a dark place and inferior to that in a
reflective liquid crystal display in a bright place. Therefore, it
is necessary to further improve image quality for using it as a
mobile information terminal.
Furthermore, displays are used in a wide variety of private and
commercial applications including information terminals such as
mobile devices, e.g., a cell phone and a PDA (Personal Digital
Assistant), digital cameras and digital video cameras, which are
used in various places. Thus, such display apparatus are required
to be robust.
Properties needed in a display panel for a mobile device include,
in addition to image quality described above, a display size, panel
thinness and power consumption.
Robustness leads to a thinner panel. Furthermore, it is necessary
to use a substrate resistant to impact. In terms of a thickness of
a panel, an organic EL display can be thinned to a thickness of one
substrate in principle. In contrast, for a liquid crystal display
panel, a reflective liquid crystal display can be thinned to a
thickness of two substrates, while a transmission/semi-transmission
type liquid crystal display inevitably becomes thicker because it
requires a backlight.
There will be discussed factors other than image quality, including
an overall dimension, a weight, robustness, power consumption and a
price. In terms of an overall dimension and a weight, an organic EL
display is overwhelmingly advantageous, which does not need a light
source such as a backlight. It can be theoretically thinned and
weight-reduced substantially to a level of one supporting substrate
by effective sealing technique. Without incorporating an auxiliary
light source, a reflective liquid crystal display panel can be
thinned and weight-reduced to a level of two supporting substrates.
However, it is still less advantageous in comparison with an
organic EL display.
These devices exhibit substantially equivalent robustness as long
as the same substrate is used. A reflective liquid crystal display
is advantageous in terms of power consumption. However, when it is
equipped with an auxiliary light source, it is comparable to a
transmissive liquid crystal display or organic EL display.
In a semi-transmissive liquid crystal display, power consumption
can be reduced in a bright place by turning a backlight off.
Furthermore, a liquid crystal display has a longer history of
commercial production than an organic. EL display, and therefore
more advantageous in terms of a price.
In a liquid crystal display with the best performance, visibly
perceptible fineness and the number of colors have substantially
reached the upper limit. Further improvement in image quality is,
therefore, insignificant. Thus, current research activities have
been also focused on improvement performance factors other than
image quality.
For example, by low-temperature polysilicon thin-film transistor
(poly-Si TFT) technique, an electronic circuit which has been
conventionally provided as an external device can be integrated on
a glass substrate. Thus, in a liquid crystal display, the number of
parts has been reduced, a frame has been narrowed and power
consumption has been reduced. Studies on a liquid crystal display
comprising a plastic substrate in place of a conventional glass
substrate have been conducted, pursuing film thinning,
weight-reduction and toughness to falling.
An organic EL display may be more promising than a liquid crystal
display in terms of thinness, weight reduction and higher
visibility, and thus have been studied for improvement in emission
efficiency and a life.
As described above, a plasma display, a transmissive liquid crystal
display or an organic EL display are suitable for stationary
applications while a semi-transmissive liquid crystal display is
suitable for mobile applications.
In the light of suitability for both stationary and mobile
applications, it can be found that a liquid crystal display has
advantages which a plasma display or organic EL display does not
have.
FIG. 27 shows a cross-sectional view of a conventional
semi-transmissive liquid crystal display panel. A liquid-crystal
panel has a configuration that a liquid crystal is sandwiched by
two substrates as shown in the upper par of FIG. 27. On one side of
one glass substrate 312, there are regularly arranged pixels
comprising a thin-film transistor 311 and a pixel electrode 310,
and there is formed an interconnection for transferring a signal
for driving the thin-film transistor 311. The pixel electrode 310
is designed to have a transmittance of 30 to 70%; often a
transmittance of 70%.
On one side of the other glass substrate 304, there is arranged a
color filter 305. The color filter (CF) 305 and a black matrix (BM)
are disposed, facing a pixel electrode and a border between pixel
electrodes, respectively, and covered by a transparent electrode
307. On the surfaces of these two substrates, there are formed
oriented films 307, 309, respectively, for orienting a liquid
crystal to a desired direction. These two substrates are fixed by a
sealing material B disposed on the periphery of the substrates. A
liquid crystal fills the space between these two substrates.
On the outer surfaces of each of these two substrates sandwiching
the liquid crystal, there is attached a film substrate having
various optical functions. In this figure, two film substrates,
i.e., a polarizing plate (linear polarizing plate) 302, 314 and a
retardation film (1/4 wavelength plate) 303, 313, are laminated for
converting an incident light into a circularly-polarized light.
Furthermore, there is provided an antireflective plate 301 for
preventing reflection of an outside light.
When applying the sealing material B, an opening is left for later
injecting a liquid crystal. Spacers corresponding to a given space
distance (for example, about 6 .mu.m) are distributed for
maintaining the given distance between these two substrates. The
spacers are considerably smaller than a pixel electrode. After
firing them under a certain load, a liquid crystal is injected from
the opening in the sealing material. Finally, the opening in the
sealing material is sealed with a UV-curable material to provide a
liquid-crystal panel.
The lower part of FIG. 27 shows a configuration of a backlight.
The backlight comprises a light source C emitting a white light
such as a lamp and a light-emitting diode (LED), an optical guide
317, a reflection plate 318, a diffusion sheet 316 and a
field-angle regulating sheet 315.
A configuration of these components is optimized to allow the
backlight to operate as a plane light emitter as even as possible
and to guide a light from the light source C toward a
liquid-crystal panel as efficiently as possible. In general, an
optical guide is a transparent plastic substrate made of polymethyl
methacrylate (PMMA) with a thickness of, for example, about 1.0 mm.
The reflection plate 318, the diffusion sheet 316 and the
field-angle regulating sheet 315 have been processed to effect
individual optical functions. Thus, the overall thickness of the
backlight components in FIG. 27 is about 2.0 mm.
There will be described operation of a semi-transmissive liquid
crystal display as a transmissive liquid crystal display with
reference to FIG. 27.
A white light from the light source C enters the optical guide 317,
alters its path by the reflection plate 318 and then is diffused by
the diffusion sheet 316. The diffused light is adjusted by the
field-angle regulating sheet 315 to have a desired orientation and
then reaches the liquid-crystal panel.
Although this light is non-polarized, only one linearly-polarized
light passes through the straight polarizing plate 314 in the
liquid-crystal panel. The linearly-polarized light is converted
into a circularly-polarized light by the retardation film (1/4
wavelength plate) 313, and sequentially passes through the glass
substrate 312, the pixel electrode 310 made of a semi-transparent
material, finally to the liquid crystal layer 308.
Orientation of the liquid crystal molecules are controlled,
depending on the presence of a potential difference between the
pixel electrode 310 and the opposite transparent electrode (counter
electrode) 306. That is, in an extreme orientation state, a
circularly-polarized light entering from the lower part of FIG. 27
is transmitted, as it is, through the liquid crystal layer 308 and
then through the transparent electrode 306. Then, a light with a
particular wavelength is transmitted through the color filter 305
to the retardation film (1/4 wavelength plate) 313. Thus, it
substantially completely passes through the polarizing plate
(straight polarizing plate) 314. The pixel, therefore, most
brightly displays a color determined by the color filter.
In contrast, in another extreme orientation state, polarity of a
light passing through the liquid crystal layer is altered, so that
a light passing through the color filter is substantially
completely absorbed by the retardation film (1/4 wavelength plate)
303 and the polarizing plate (straight polarizing plate) 302. Thus,
the pixel displays black color. In an intermediate orientation
state between these two states, a light is partially transmitted,
so that the pixel displays an intermediate color.
Next, there will be described operation of a semi-transmissive
liquid crystal display as a reflective liquid crystal display.
When an outside light enters a liquid-crystal panel from the upper
part of FIG. 27, a circularly-polarized light which has been
transmitted through the polarizing plate (straight polarizing
plate) 302 and the retardation film (1/4 wavelength plate) 303,
passes through a liquid crystal layer. Then, 30% of the light is
reflected by a pixel electrode to be utilized for displaying.
Therefore, the display operates as a reflective liquid crystal
display.
Next, there will be described operation of a semi-transmissive
liquid crystal display.
In a semi-transmissive liquid crystal display, a pixel electrode is
made of a semi-transparent material and its operation as a
transmissive liquid crystal display is as described above, although
when designing a light transmittance in the pixel electrode to, for
example, 70%, 30% of the light is not used for displaying. On the
other hand, when an outside light enters the liquid-crystal panel
from the upper part of FIG. 27, a circularly-polarized light which
has been transmitted through the straight polarizing plate and the
1/4 wavelength plate passes through a liquid crystal layer and 30%
of the light is reflected to be utilized for displaying. It,
therefore, operates as a reflective liquid crystal display.
In the prior art, a substrate constituting a thin-film transistor
has been a glass substrate which can tolerate an high-temperature
during manufacturing the thin-film transistor. On the other hand,
there has been investigated technique for forming a thin-film
transistor at a lower temperature. For such technique, device
properties are not adequate for forming a functional device on the
substrate on which a thin-film transistor for driving a liquid
crystal is formed, in response to the recent need for size
reduction. Thus, the technique has not been practically used.
Thin-film transistors can be classified into three categories:
high-temperature polysilicon transistors formed on a quartz
substrate, low-temperature polysilicon transistors formed on a
glass substrate and amorphous silicon transistors formed on a glass
or plastic substrate. For size-reduction of a liquid-crystal panel,
it has been attempted to form a driver IC which has been
conventionally an external device, on a glass substrate. An
amorphous silicon transistor can be manufactured at a lower
temperature, but its properties adequate to operate a driver IC
cannot be practically achieved on a plastic substrate. It is,
therefore, more practical to form a low-temperature polysilicon
transistor on a glass substrate, in the current manufacturing
technique.
As shown in FIG. 28, a transmissive liquid crystal display
utilizing a plastic substrate has been experimentally manufactured
as described by Asano et al. (A. Asano and T. Kinoshita,
"Low-temperature polysilicon TFT color LCD panel made of plastic
substrates," in Society for Information Display International
Symposium Digest of Technical Papers (Society for Information
Display, Boston, 2002,) Vol. 33, pp. 1196-1199.).
According to the above paper, on a glass substrate comprising an
antietching layer is formed, by a well-known process for
manufacturing a low-temperature polysilicon thin-film transistor, a
polysilicon TFT, on which is then applied a removable adhesive,
through which is then glued a temporary substrate (FIG. 28(a)).
Next, the glass substrate is etched off by hydrofluoric acid (HF)
(FIG. 28(b)). Then, after removing the antietching layer, a
polysilicon TFT is glued via an adhesive to a plastic substrate
with a thickness of 0.2 mm (FIG. 28(c)). Subsequently, the
temporary substrate and the removable adhesive are sequentially
removed (FIG. 28(d)). Next, the substrate and a substrate
comprising, for example, a color filter and a transparent electrode
are disposed, facing each other. Liquid crystal molecules are
injected into the space between the substrates to form an active
driving liquid crystal display panel.
A conventional transmissive/semi-transmissive liquid crystal
display is thick and heavy because it uses a backlight. For solving
the problem, there has been proposed a configuration using an
organic EL.
JP-2000-29034-A and JP-2002-98957-A have disclosed a configuration
using an organic EL as a backlight, which will be described below
with reference to FIG. 29.
JP-2000-29034-A shown in FIG. 29A has described that in order to
prevent an organic EL from being deteriorated due to a high
temperature during forming an oriented film by a conventional
firing process, an oriented film 623 which has been preliminarily
oriented is laminated with a display-driving substrate 621 and a
counter substrate 622.
The liquid crystal display panel in FIG. 29A is manufactured as
follows. First, a TFT array substrate 621 and a counter substrate
622 comprising a plane light emitter which is produced by separate
processes are laminated. Then, the product is subject to common
rubbing to provide the polymer film with an orientating function to
the liquid crystal composition 624 to form an oriented film 623.
Then, the TFT array substrate 621 and the oriented film 623 to the
counter substrate 622 are disposed, facing each other. Then, the
space between them is filled with a liquid crystal composition
624.
In the structure in FIG. 29A, an organic film is laminated with the
oriented film according to the prior art as shown in FIG. 27, and a
backlight is replaced with an organic EL. Although a substrate for
forming the organic EL is needed, a glass substrate has a thickness
of 0.4 mm while a conventional optical guide has a thickness of
several mm. Thus, it results in reduction in a film thickness.
JP-2000-98957-A has disclosed that in a transmissive liquid-crystal
panel, an organic EL light-emitting device is used in place of a
conventional fluorescent tube as a backlight for reducing a film
thickness and a weight. FIG. 29B shows its structure.
The liquid crystal display panel comprises a first electrode
substrate 650, a second electrode substrate 660 and a liquid
crystal layer between these substrates.
The first electrode substrate 650 is comprised of a transparent
glass substrate 651, whose surface to be in contact with a liquid
crystal layer, comprises a scan line 652, a signal line 653 (not
shown), a pixel electrode 654, a TFT 655, an auxiliary capacity 656
(not shown) and an auxiliary capacity line 657.
In the second electrode substrate 680, a transparent glass
substrate 681 has a surface to be in contact with a liquid crystal
on which a transparent electrode 682 to be a counter electrode to a
liquid crystal and a surface facing the surface comprising
substrate transparent electrode 682 in the glass substrate 681
comprises emitting parts 683, 685, 687, 689 in an organic EL and
non-emitting parts 684, 686, 688 as spaces between the emitting
parts 683, 685, 687, 689.
FIG. 29B shows that a film thickness can be reduced by eliminating
an optical guide for a backlight which has been required in the
prior art, by means of forming a plane light-emitting device
consisting of an organic EL on the rear surface of the substrate
comprising a counter electrode in a liquid-crystal panel. Thus, the
number of substrates can be reduced to two while the conventional
configuration needs three substrates as shown in FIG. 29A,
resulting in thickness reduction in a liquid-crystal panel.
JP-54-126559-A has disclosed the use of a long flexible film as a
substrate in a liquid-crystal panel. The application has, however,
disclosed only an example where a long flexible film comprising a
transparent electrode and an oriented film is used to form a simple
matrix driving type of a monochrome liquid-crystal panel. The
technique disclosed in JP-54-126559-A is related to manufacturing a
liquid-crystal panel using a long plastic substrate in the era when
a large and flat glass substrate was expensive and could not be
easily produced. Furthermore, JP-62-150218-A and JP-06-27448-A have
disclosed that a liquid crystal fills a space between long flexible
films in which oriented films are formed on two electrodes.
However, a liquid-crystal panel had been required to be colorized
and to display a movie. In order to increase a response speed,
active matrix driving has been dominant as a driving system, where
pixels in a liquid crystal are directly driven by a thin-film
transistor. Furthermore, color displaying needs, in addition to an
oriented film, other optically functional films such as a
retardation film and a polarizing film. Additionally, as
improvement in display visibility has been needed, there have been
developed various types of liquid-crystal panels such as
transmissive, reflective and semi-transmissive panels. Thus, the
above technique could not respond to these.
Although there were problems of size increase and flatness in a
glass substrate around 1975, these problems have been overcome by
improvement in manufacturing technique for a glass substrate, and
it is believed that a glass substrate is optimal for an active
driving type liquid-crystal panel using a thin-film transistor.
In various types of liquid-crystal panels such as transmissive,
reflective and semi-transmissive types, it is necessary to laminate
a plurality of optically functional films with a substrate. In this
process, the films are laminated one by one with the liquid-crystal
panel, so that it requires many steps of laminating the optically
functional films.
For simplifying the lamination process, JP-2002-358024-A and
JP-2002-148607-A have disclosed that a long flexible film is
laminated with a glass substrate. Patent document 1 JP-2000-29034-A
Patent document 2: JP-2002-98957-A Patent document 3 JP-54-126559-A
Patent document 4 JP-62-150218-A Patent document 5:
JP-2002-358024-A Patent document 6: JP-2002-148607-A Nonpatent
literature 1: A. Asano and T. Kinoshita, "Low-temperature
polysilicon TFT color LCD panel made of plastic substrates," in
Society for Information Display International Symposium Digest of
Technical Papers (Society for Information Display, Boston, 2002,)
Vol. 33, pp. 1196-1199.
DISCLOSURE OF THE INVENTION
Problems to be Resolved by the Invention
As described above, a liquid-crystal panel has a structure where a
liquid crystal is sandwiched between electrodes. Thus, it is
necessary to form a driving electrode and a counter electrode on
separate substrates.
Conventionally, since a TFT (thin-film transistor) requires a high
temperature heat treatment, it has been believed that using a glass
substrate is essential. It has been, however, indicated that a
plastic substrate may be used by employing the method as described
by Asano et al.
A liquid crystal can be prepared by a known method. A
liquid-crystal panel is manufactured by laminating one substrate
comprising a driving electrode and the other substrate comprising a
counter electrode, on both of which there are disposed films having
functions such as light polarization, forming phase difference and
orientation.
A backlight is manufactured by a step other than that for the
liquid-crystal panel, and then disposed on the rear surface of the
liquid-crystal panel.
A configuration of a semi-transmissive or transmissive
liquid-crystal panel requires three substrates even when using an
organic EL as a backlight and a TFT is manufactured as described by
Asano et al. Consequently, the liquid-crystal panel and the
backlight have thicknesses of about 0.4 mm and about 0.2 mm,
respectively, leading to the minimum overall thickness of 0.6
mm.
There have been strong needs for a thin-film and light-weight
display panel. Thus, E Ink Corporation (U.S.A) has developed an
active matrix type device with a thickness of 3 mm, one tenth of a
liquid crystal display panel, using an electron ink.
A liquid crystal display panel is composed of optically functional
films laminated on a rectangular substrate (a glass substrate or
plastic substrate). When using a rectangular substrate, the
following problem is inevitable.
A liquid crystal display is needed to have a wide range of display
size, from 2.1 inches for a cell phone to 15, 17 inches for a
personal computer, and from 17 inch wide to 40 inch wide for a
television. Since it is difficult to construct a production line
for each substrate size, a rectangular large-area substrate must be
used.
The step of forming a liquid crystal display is similar to the step
of forming a semiconductor device on a silicon wafer. Since
productivity is improved when forming many sheets on one base in
sheet processing, the step has become larger-scaled. In contrast to
a semiconductor apparatus with a size of several centimeters, a
liquid crystal display may have a diagonal size of more than 40
inches. Thus, there has been proposed a glass substrate as a base
with a size of larger than 1 m.times.1.5 m.
The production line must use a rectangular large-area substrate for
responding to various sizes.
A liquid-crystal panel has a configuration where films having an
optical function (hereinafter, referred to as "optically functional
film") are placed one by one on a substrate comprising a TFT and/or
a substrate comprising a counter electrode. In the liquid-crystal
panel shown in FIG. 27, the two substrates sandwiching the liquid
crystal have one surface comprising an oriented film facing the
liquid crystal and the other surface comprising optically
functional films such as a retardation film and a polarizing film
(plate).
These films must be placed one by one on the substrate, leading to
a longer production step and a longer turn around time (TAT) in the
manufacturing process.
When using a rectangular substrate, a substrate is carried one by
one or from a cassette. However, the following problem has become
significant as a substrate size has been increased to over
1.5.times.1.5 m.sup.2.
For a glass substrate, (1) a sheet is carried while supporting the
lower surface of the glass, so that a larger size of a glass
substrate has led to significant increase in an area for placing an
apparatus, resulting in the need of a huge manufacturing facility.
For cassette carrying, a cassette which can be inserted with a
space for avoiding mutual contact between substrates, but carrying
becomes difficult as the cassette becomes larger and heavier. (2)
Conventionally, although a glass substrate has been thinner,
further thinning of the substrate cannot be achieved when the
substrate become heavier in association with size increase. As
occurs in a manufacturing line for a semiconductor integrated
circuit, it may even lead to increase in a substrate thickness.
When using a plastic substrate, (1) the plastic substrate is
flexible, so that, for example, it may not be inserted into a
processing apparatus without designing the apparatus taking flexure
during carrying into account.
There has been proposed that a plastic substrate is laminated with
a hard substrate such as glass. However, this may lead to the same
problem in (1) where a glass substrate is used. Furthermore, it
leads to increase in the number of steps such as lamination and
peeling, and the use of a glass substrate may result in increase in
a material cost.
As a liquid-crystal panel becomes larger or more displays with a
smaller size are taken, a substrate becomes thicker. On the other
hand, there are needs for thinning a mobile display device whose
applications are diverse, e.g., outdoor and indoor, bright and dark
places, fine and rainy weather, etc.
When a large substrate is used for responding to thinning of a
substrate, a manufacturing apparatus is required to be more
precise, leading to an expensive apparatus. Thus, it may cancel
cost reduction in manufacturing a liquid-crystal panel by size
increase in a substrate.
Furthermore, a conventional semi-transmissive liquid crystal
display panel is designed such that a pixel electrode has a
transmittance of, for example, about 0.3 to 0.7 to ensure good
visibility in both bright and dark places. Therefore, in comparison
with a reflective liquid crystal display having the same pixel
area, a utility efficiency of outside light is reduced in a
semi-transmissive liquid crystal display, leading to dark display.
Furthermore, in comparison with a transmissive liquid crystal
display with the same pixel area, a utility efficiency of a light
from a backlight is reduced, leading to dark display. In other
words, a conventional semi-transmissive liquid crystal display has
the problem that a light utility efficiency is lower and display is
darker than a reflective liquid crystal display or a transmissive
liquid crystal display.
In view of the situation, this invention has been designed.
Specifically, an objective of this invention is to provide a
thin-shaped liquid crystal display panel. Another objective of this
invention is to reduce a manufacturing cost for a liquid crystal
display panel by simplifying a manufacturing process.
Means of Solving the Problems
According to this invention, there is provided a light-condensing
film, wherein an array of light collectors made of an organic resin
is formed on a long light-diffusing film with a flexibility of 40
mm or less of a curvature radius and a coefficient of thermal
expansion of 50 ppm/.degree. C. or less and a surface in the light
collector facing the surface contacting with the film is flat and
has a smaller area than the surface contacting with the film. The
light-diffusing film preferably has a Young's modulus of 1.5 GPa or
more.
The light-diffusing film is fed from a first roll to a second roll,
during which a thin film can be formed on its surface. Furthermore,
to a thermal history at 200.degree. C., variation in mechanical and
optical properties is preferably .+-.5% or less, and to a thermal
history at 250.degree. C., mechanical and optical variation is
preferably .+-.5% or less.
The light-diffusing film preferably comprises transparent
light-diffusing particles with a refractive index different from
that of the film. Preferably, the transparent particle is zinc
oxide, ITO or silica and has a particle size of 0.5 .mu.m or more
and 1/2 or less of the film thickness.
The light-diffusing film and the light collector are preferably
made of the same resin. Furthermore, the resin is preferably
selected from an acrylic resin and a cyclic olefin resin.
The light-condensing film may be laminated, on the surface facing
the light diffusing film in the light collector in the above
light-condensing film, with a long light-guiding film having a
coefficient of thermal expansion of 50 ppm/.degree. C. or less.
The light-guiding film preferably has a Young's modulus of 1.5 GPa
or more.
Furthermore, the light-guiding film is fed from the first roll to
the second roll, during which a light-condensing film comprising a
light collector on a light diffusing layer can be laminated with
the surface facing the light diffusing film in the light
collector.
In terms of the light-guiding film, variation in mechanical and
optical properties is preferably .+-.5% or less to a thermal
history at 200.degree. C., more preferably .+-.5% or less to a
thermal history at 250.degree. C.
The light-guiding film preferably comprises an inorganic fillers,
which preferably has a particle size of 1 nm to 380 nm.
The inorganic fillers is preferably made of a material selected
from titanium dioxide, zinc oxide, alumina and silicon oxide.
Furthermore, the light-guiding film preferably has a light
transmittance of 80% or more.
The light-guiding film is preferably made of an acrylic resin or a
cyclic olefin resin.
Furthermore, the light-diffusing film, the light collector and the
light-guiding film are preferably made of the same resin, which is
preferably selected from an acrylic resin and a cyclic olefin
resin.
There is provided a functional film comprising an optically
functional thin film formed on a light-diffusing film in a
light-condensing film comprising the light-diffusing film, a light
collector and a light-guiding film; a transparent counter electrode
in a liquid crystal device; and an oriented film on the counter
electrode. The functional film and each oriented film in a
functional film comprising a liquid crystal functional thin film
comprising, for example, a pixel electrode for a liquid crystal, an
optically functional thin film and the oriented film are disposed,
facing each other. Then, a liquid crystal can be sandwiched between
the oriented films to form a liquid-crystal panel.
The light-condensing film comprising the light-diffusing film, the
light collector and the light-guiding film is divided into desired
shape pieces, and then a light source is placed adjacently to at
least one plane substantially perpendicular to the plane on which
the light collector in the optical guide is placed, to form a
backlight.
According to another aspect of this invention, there is provided a
process for manufacturing a light-condensing film comprising the
steps of filling an irregularity in a support corresponding to the
irregularity of the light collector with an organic resin and
transferring the filling resin to the long light-diffusing thin
film.
According to another aspect of this invention, there is provided a
process for manufacturing a light-condensing film comprising the
steps of forming a thin film made of an organic resin on a long
light-diffusing film and transferring the shape of the light
collector to the thin film.
The step of transferring the shape of the light collector can be
conducted by pressing a template having an irregularity
corresponding to the shape of the light collector.
The step of transferring the shape of the light collector may
optionally comprise the step of curing the organic resin under
pressure. The organic resin can be cured by UV-ray irradiation.
The process may comprise the step of depositing a light-guiding
thin film on the light collector.
This invention is characterized in that various thin films
constituting a liquid-crystal panel and/or a backlight are formed a
flexible base film by transfer using a roll-to-roll process.
This invention is particularly characterized in that a backlight
comprising an optical guide can be manufactured by a roll-to-roll
process.
In this invention, transfer is conducted between films, so that
intermittent operation can be eliminated during transfer between a
substrate and a film, resulting in a simplified configuration of a
transfer apparatus. Furthermore, when using substrates, transfer
must be conducted for each substrate. It is, therefore, necessary
to form a functional thin film on a film in conformity to the size
of the substrate or to separate a functional thin film after
transferring to the substrate.
When forming a variety of functional thin films directly on a base
film, a resin constituting an optically functional thin film is
cured by heating or light irradiation. If a cured resin is exposed
to further heating or light irradiation, the cured resin may be
decomposed or deteriorated due to further curing. Thus, the optimal
curing conditions cannot be chosen for some materials.
According to this invention, each functional thin film can be
formed under the optimal conditions for the film because heating
during transferring is at a lower temperature and for a shorter
period, so that the functional thin film is not deteriorated.
Various functional thin films formed on a supporting film as a
flexible base film using a roll-to-roll process have a flexibility
equivalent to that of the base film. As a result, the functional
thin films constituting a liquid-crystal panel is not peeled by
bending of the substrate. When matching a coefficient of thermal
expansion between the base film and the supporting film, there is
not generated stress due to expansion coefficient difference
between the films in a functional thin film transferred to the base
film. Thus, the cause for peeling of a transferred film can be
eliminated.
Furthermore, using an optical guide as a backlight also contributes
to weight reduction in a liquid-crystal panel, and the panel has a
flexibility equivalent to the base film, so that impact such as
falling can be absorbed by bending of the base film as a substrate,
resulting in significant improvement in shock resistance.
When this invention is applied to a display in a device such as a
mobile display which is supposed to be used in substantially all
places, damage in the display can be minimized.
The panel can be manufactured while forming a plurality of
functional thin films on a film by a roll-to-roll process. Even
when manufacturing a large-sized display panel or a number of
display panel from one sheet of substrate, it can be carried while
being wound-up as a roll. It can be, therefore, carried between
apparatuses in a narrow space, and accidents such as breakage
during carrying can be prevented.
Furthermore, even when a liquid-crystal panel is large-sized, it is
not necessary to increase a thickness of a film to be an optical
guide, so that thinning or weight reduction in the liquid-crystal
panel is not be inhibited.
In a conventional glass substrate, bending in a substrate caused by
a difference in a coefficient of thermal expansion between the
substrate and an optically functional thin film formed on the
substrate due to a hardness of a glass substrate has not been a
significant problem. It is anticipated that bending due to a
difference in a coefficient of thermal expansion in a substrate
will occur when a glass substrate becomes further thinner or a
plastic substrate is used, substrate.
In this invention, since a functional film and a substrate (base
film) as a main component in a backlight are made of the same
material, bending in a liquid-crystal panel due to a difference in
a coefficient of thermal expansion between materials can be
prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a conceptual view of a manufacturing process according to
this invention.
FIG. 2 is a conceptual view of a manufacturing process according to
this invention.
FIG. 3 is a conceptual view illustrating a process for transferring
a polarizing film and a retardation film according to this
invention.
FIG. 4 is a conceptual view illustrating a process for
manufacturing a liquid-crystal panel according to this
invention.
FIG. 5 shows a structure of a base film according to this
invention.
FIG. 6 is a schematic view showing a manufacturing process for an
oriented film and a process for transferring the oriented film.
FIG. 7 is a cross-sectional structural view of an organic EL device
according to this invention.
FIG. 8 is a conceptual view of an apparatus for manufacturing a
barrier film on a base film, according to this invention.
FIG. 9 is a process cross-sectional view illustrating a process for
manufacturing a thin-film transistor according to this
invention.
FIG. 10 is a process cross-sectional view illustrating a process
for transferring a thin-film transistor according to this
invention.
FIG. 11 is a conceptual view illustrating a process for
manufacturing a color filter according to this invention.
FIG. 12 is a conceptual view illustrating a process for
manufacturing a color filter according to this invention.
FIG. 13 is a conceptual view illustrating a process for
manufacturing a color filter according to this invention.
FIG. 14 is a cross-sectional structural view of a liquid-crystal
panel according to this invention.
FIG. 15 shows a process for manufacturing a liquid-crystal
panel.
FIG. 16 is a cross-sectional structural view of a liquid-crystal
panel according to this invention.
FIG. 17 is a conceptual view illustrating a process for
manufacturing a liquid-crystal panel according to this
invention.
FIG. 18 is a cross-sectional structural view of a liquid-crystal
panel according to this invention.
FIG. 19 is a cross-sectional view of a transfer roller for forming
an irregularity in a thin film.
FIG. 20 shows an apparatus for measuring reflection properties.
FIG. 21 is a cross-sectional view of a reflection film having a
concave curve structure.
FIG. 22 shows a relationship between a pitch and a height in an
irregularity indicating good properties of a reflection film having
a concave curve structure.
FIG. 23 is a cross-sectional view of a reflection film having
concave-convex combined curve structure.
FIG. 24 shows a relationship between a pitch and a height in an
irregularity indicating good properties of a reflection film having
a concave-convex combined curve structure.
FIG. 25 shows a method for flattening a surface of a reflection
film having an irregular surface.
FIG. 26 is a structure cross-sectional view of a liquid-crystal
panel comprising a reflection film having an irregular surface.
FIG. 27 is a cross-sectional structural view of a liquid-crystal
panel according to the prior art.
FIG. 28 is a process-explanatory view illustrating a process for
transferring a TFT according to the prior art.
FIG. 29 is a cross-sectional structural view of a liquid-crystal
panel according to the prior art.
FIG. 30 shows a rear light source using an optical guide.
FIG. 31 shows a shape of a light collector.
FIG. 32 is an overhead view of a light collector array.
FIG. 33 shows a process for manufacturing a light collector.
FIG. 34 shows a process for manufacturing a light collector.
FIG. 35 shows a process for manufacturing a light collector.
FIG. 36 shows a structure of a light diffusing film and a light
collector array.
FIG. 37 shows a structure of a light diffusing film and a light
collector array.
FIG. 38 shows a structure of a light diffusing film and a light
collector array.
FIG. 39 is a cross-sectional view of a liquid-crystal panel.
FIG. 40 shows a process for manufacturing a liquid-crystal
panel.
FIG. 41 shows a process for manufacturing a liquid-crystal
panel.
FIG. 42 shows a process for manufacturing a liquid-crystal
panel.
In these drawings, the symbols have the following meanings; 1:
vacuum chamber, 2: wind-off roll, 3: base film, 4: exhaust pump, 5:
target, 6: exhaust pump, 7: temperature-controlling drum, 8:
reactant gas inlet tube, 9: discharge gas inlet tube, 10: exhaust
pump, 11: wind-up roll, 100: polarizing film, 101: functional film
A, 102: matrix base, 103: optically functional layer, 104:
functional film B, 105: base film, 106: opaque electrode, 107, 110:
organic EL layer, 111: cover film, 112: functional film, 113:
polarizing film, 115: supporting film, 116: retardation film, 151:
oriented film, 152: UV-ray source, 153: polarized filter, 154: base
film, 155: transistor layer, 321: display-driving substrate, 323:
oriented film, 322: counter substrate, 324: liquid crystal
composition, 351: anti-reflection film, 352: polarizing film, 353:
retardation film, 354: base film, 355: color filter, 356:
transparent electrode, 357: oriented film, 358: liquid crystal,
359: oriented film, 360: pixel electrode, 361: interconnection,
thin-film transistor, 362: base film, 363: retardation film, 364:
polarizing film, 365: transparent electrode, 366: organic EL layer,
367: reflection electrode, 368: base film, 371: second functional
film, 372: first functional film, 373: matrix base, 374: matrix
base, 375: device layer, 376: optically functional thin film, 377:
third functional film, 380: base film, 381: TFT layer, 390: base
film, 391: photosensitive resin, 392: cover film, 393: CF base,
394: black matrix, 395: R (red), 396: G (green), 397: B (blue),
398: spacer, 399: color filter, 401: base film, 402: thin-film
transistor, interconnection, 403: pixel electrode, 404: color
filter, 405: oriented film, 406: liquid crystal, 407: oriented
film, 408: counter electrode, 409: retardation film, 410:
polarizing film, 411: transparent electrode, 412: organic EL layer,
413a: transparent electrode, 413: reflection film, 414b: flattening
film, 414a: film, 414: base film, A: spacer, 451: base film, 452:
transistor layer, 453: supporting film, 454: color filter, 455:
spacer, 456: oriented film, 621: display-driving substrate, 623:
oriented film, 622: counter substrate, 624: liquid crystal
composition, 650: first electrode substrate, 660: second electrode
substrate, 654: transparent electrode, 655: TFT, 682: transparent
electrode, 683, 685, 687, 689: emitting part, 684, 686, 688:
non-emitting part, 701: optical guide, 702: reflection film, 703:
light collector array, 704: light diffusing film, 705: light
source, 706: light-emitting diode, 707: resin, 708: supporting
film, 709: UV-curable resin, 710: UV-irradiation apparatus, 711:
light-diffusing material, 712: light-diffusing layer, 713: liquid
crystal, 714: sealing material, 715: counter base film, 716: liquid
crystal cell, 717: base film with a collector array, 718: optical
guide, 719: precise cutting, 720: rough cutting, 721: lamination,
801: forming a barrier layer, 802: forming a retardation layer,
803: forming a polarizing layer, 804: transferring a TFT, 805:
forming a color filter (CF), 806: forming a reflection electrode,
807: forming an organic EL, 808: forming an upper electrode, 809:
forming a barrier layer, 810: forming a polarizing layer, 811:
forming a retardation layer, 812: forming a transparent electrode,
813: orientation treatment, 814: injecting a liquid crystal, 815:
sealing, 820: first functional film, 830; second functional film,
1000: base film, 1001: retardation function, 1002: polarizing
function, 1003: antireflecting function, 1010: application, 1020:
drying and cooling, 1030: applying a cover film, 1040: peeling a
cover film, 1050: transferring a polarizing film, 1060:
transferring a retardation film, 1070: applying a CF base, 1080:
exposure, 1090: peeling a base film, 1100: development and drying,
1110: applying a cover film, 1120: sealant, 1130: spacer, 1140:
temporary substrate, 1150: removable adhesive, 1160: polysilicon
TFT, 1170: anti-etching layer, 1180: glass substrate, 1190:
adhesive, 1200: plastic substrate, 2000: transfer roller, A:
polymerization, B: outgoing light, BU: blue, C: laser beam, D:
boron ion doping, E: phosphorous ion doping, F: p-type area, G:
etching, GR: green, BM: black matrix, and R: red.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
According to this invention, a liquid-crystal panel is manufactured
by forming optically functional films, a TFT device and a light
emitting device on thin films consisting of a long substrate made
of an organic resin, which are then laminated.
A liquid-crystal panel according to this invention has a
configuration such as those illustrated in FIGS. 14, 16 and 18. The
liquid-crystal panel comprises a flat light emitting device unit to
be a backlight and a liquid crystal device unit. The configuration
will be generally described with reference to FIG. 14. In FIG. 14,
the flat light emitting device unit constituting a backlight is a
backlight using a light-condensing film according to this
invention.
The light-condensing film has a configuration similar to that using
a conventional optical guide, having advantages that it can be
thinner than an optical guide and that a well-established light
source can be used.
The backlight comprises a functional film capable of collecting a
light (light-condensing film) and a light source. The
light-condensing film is a laminated film in which a light
collector 366 and a supporting film 365 are formed on a base film
368. The light source is formed on the side surface of the
light-condensing film.
In the above light-condensing film of this invention, an array of
light collectors made of an organic resin are formed on a
light-diffusing film, and a light-guiding film (hereinafter,
sometimes referred to as an "optical guide") together with a
laminated light source disposed at the end constitutes the
backlight.
In the liquid crystal device unit, on one side of a first base film
362, there are formed a retardation film 363 and a polarizing film
364 as optically functional thin films which have an optical
function. On the other side of the first base film 362, there are
laminated an interconnection, a thin-film transistor 361 and a
pixel electrode 360 involved in some functions of a laminated
liquid crystal device, and a device functional thin film consisting
of an oriented film 359.
One side of the second base film 354 constituting the liquid
crystal device unit comprises a retardation film 353, a polarizing
film 352 and an anti-reflection film 351 as optically functional
thin film which are optically functional. In the other side of the
second base film, there is laminated a device functional thin film
comprising a color filter 355, a transparent electrode 356 and an
oriented film 357, which is involved in some of functions of the
liquid crystal device.
The liquid crystal device unit is formed by facing the oriented
film 359 in the first functional film where the optically
functional thin films and the device functional thin film are
laminated and an oriented film 357 in a second functional film via
a space and filling the space with a liquid crystal 358.
These optically functional thin films having optical functions and
a device functional thin film involved in some functions of a
device are laminated on, for example, a supporting film other than
a base film during a manufacturing process. These films are
collectively referred to as "functional films". Optically
functional thin films or device functional thin films formed on
such a functional film are collectively referred to as "functional
thin films".
In addition to an interconnection, a thin-film transistor and a
pixel electrode, an active device and/or a passive device may be
formed. Furthermore, since an interconnection, a thin-film
transistor, a pixel electrode and other active and passive devices
may not be formed in one layer, each of these layers may be called
a "device functional thin film".
It will be clearly understood that a backlight may be an organic EL
device or inorganic EL device which a light emitting device is
formed on its surface and can be thinned, instead of the above
light-condensing film, and that a light may not be necessarily
emitted from its overall surface. For example, even a vertical
cavity surface emitting laser diode (VCSEL) or resonant cavity
light emitting diode (RCLED) can be of course used as long as it
can be formed as a thin film.
A color filter or oriented film may be called a device functional
thin film having a device function from operation of a
liquid-crystal panel, and also may be called an optically
functional thin film having an optical function.
It will be clearly understood that a device functional thin film
and an optically functional thin film are not limited to these
examples, but may be varied, depending on a configuration of a
liquid-crystal panel.
Embodiment 1 of this invention will be described with reference to
FIG. 1. FIG. 1 is a conceptual view illustrating a process for
manufacturing a liquid-crystal panel using a long film made of an
organic resin. While applying a tension for preventing shrinkage, a
base film wound-up as a roll is fed from a wind-off roll to a
wind-up roll. In the course of the process, the base film is
sequentially endowed with various functions such as retarding
function and polarizing function, to form a functional film A
having optical functions.
FIG. 2A is a conceptual view illustrating a process for forming a
device function on a base film, where an organic EL light emitting
device is formed on the base film On a base film 105 fed from a
wind-off roll is formed an opaque electrode layer by physical vapor
deposition and a light-emitting layer consisting of an organic EL
layer made of an organic material by deposition or application,
then a transparent electrode by physical deposition as described
for the opaque electrode and then a functional film B comprising a
light emitting device, and finally the film is wound into a wind-up
roll.
FIG. 2B is a conceptual view illustrating the step of transferring
only an optically functional layer from the functional film A
having an optical function to the functional film B comprising the
light emitting device.
The functional film B is fed to a wind-up roll from the wind-up
roll B, while in the functional film A similarly fed from a
wind-off roll, an optically functional layer 103 is peeled from a
matrix base 102 and transferred on a device layer 106 in the
functional film B. The functional film B comprising the optically
functional layer 103 transferred on the device layer 106 is then
wound into a wind-up roll.
In terms of required properties, the matrix base 102 preferably has
a coefficient of thermal expansion and flexibility comparable to
the base film. A coefficient of thermal expansion and flexibility
are preferably comparable to those in the base film. A coefficient
of thermal expansion is preferably 50 ppm/.degree. C. or less. More
preferably, a difference between its coefficient of thermal
expansion and that in the base film is preferably .+-.30% or less,
more preferably .+-.15% or less.
Matching flexibility and a coefficient of thermal expansion between
films can prevent stress accumulation on a transferred film to
avoid peeling.
A coefficient of thermal expansion can be reduced by adding
inorganic fillers. The inorganic fillers must have a size smaller
than a light wavelength for keeping transparency of the film, and
when conducting resin curing using UV rays, a particle size must be
smaller than the wavelength of UV rays needed photoUV rays used for
photo-curing often have a wavelength of 200 nm to 300 nm. Herein,
it is preferably 1 nm to 200 nm or less, more preferably 1 nm to
100 nm. If it is 200 nm or less, a photocurable film formed on the
matrix base 102 can be irradiated with UV rays having a wavelength
of 200 nm to 300 nm through the matrix base 102. Since UV rays can
be irradiated through the matrix base 102, a deposition mechanism
can be placed on the upper surface of the matrix base 102 while a
UV-ray irradiation mechanism can be placed on the lower surface of
the matrix base 102. Here, it is not necessary to place a
deposition mechanism and a UV-ray irradiation mechanism on the
upper surface of the matrix base 102. Thus, freedom in designing an
apparatus is increased, resulting in further size reduction of a
manufacturing apparatus.
Although a particle size of the inorganic fillers may be 1 nm or
less, it is difficult to prepare fillers with a size of 1 nm or
less by current technique.
The amount of the inorganic fillers is preferably 5% by weight to
90% by weight both inclusive, more preferably 10% by weight to 50%
by weight both inclusive. When it is 5% by weight or more, a
coefficient of thermal expansion can be reduced, while when it is
90% by weight or less, its fragility is acceptable.
The inorganic fillers may be added in such an amount that matching
of a coefficient of thermal expansion with the base film can be
achieved within the above range.
It is preferable that the cover film is also matched with the base
film for a coefficient of thermal expansion as is in the supporting
film.
Examples of the inorganic fillers include titanium dioxide, zinc
oxide, alumina and silicon oxide. The inorganic fillers can be
incorporated, for example, by dispersing dry powdery silicon oxide
particles using a mixer having higher dispersing ability; by
blending a colloid (sol) dispersed in an organic solvent and other
components and removing the organic solvent in vacuo optionally
with stirring; or by blending a colloid (sol) dispersed in an
organic solvent and other components, removing the solvent as
necessary and then further removing the solvent by flow casting. An
example of an apparatus having higher dispersing ability is a bead
mill.
Furthermore, when a film formed on the matrix base 102 is
deteriorated by, for example, moisture in the air (e.g., a
polarizing film), it is preferable to form a gas barrier layer on
the surface of the matrix base 102. When it is formed on one side
of the matrix base 102, it may be effective on either side, but it
may be more effective when being formed on the surface on which a
film is to be formed.
When a film is cured by UV-ray irradiation, the gas barrier layer
must be transparent to UV rays. Thus, examples of a material of the
gas barrier layer include organic materials such as polyvinyl
alcohols and polyvinylidene chlorides; organic-inorganic composite
materials such as those of an organic material with an inorganic
material including a clay mineral (an amorphous clay mineral such
as Al.sub.2O.sub.3-2SiO.sub.25H.sub.2O and
Al.sub.2O.sub.3SiO.sub.22-3H.sub.2O, or a crystalline clay mineral
such as (Si,Al)O.sub.4 tetrahedral sheet and (Al,Mg)(O,OH).sub.6
octahedral sheet); and a thin film of an inorganic material such as
silicon oxide and aluminum oxide. A film thickness may be more
reduced by using an inorganic material because it exhibits good gas
barrier properties under a high humidity atmosphere and is
effective with a smaller thickness. Furthermore, two or more of
these layers may be laminated.
An organic material may reduce a cost because a gas barrier film
can be in the form of a coating or laminated film in contrast to an
inorganic material. It is inevitably inferior to a gas barrier film
made of an inorganic material in terms of temperature dependency
and moisture resistance.
A thickness of a gas barrier layer is preferably 1 .mu.m to 10
.mu.m when it is made of an organic material or an
organic-inorganic composite material and preferably 10 nm to 1
.mu.m when it is made of an inorganic material. When it is made of
an organic material or an organic-inorganic composite material, a
thickness of 1 .mu.m or more can adequately prevent common air
components such as oxygen and moisture from entering a liquid
crystal layer or an organic EL layer. A thickness of 10 .mu.m or
less does not influence properties of the base film such as an
expansion coefficient.
When it is made of an inorganic material, a thickness of 10 nm or
more can adequately prevent common air components such as oxygen
and moisture from entering a liquid crystal layer or an organic EL
layer, while a thickness of 1 .mu.m or less can prevent breakage
during bending.
A gas barrier layer can be formed on a film by an application
method for an organic material or an organic-inorganic composite
material and by any of various film deposition methods for an
inorganic material. In an application method, a liquid such as a
liquid organic material or a solution thereof is applied on a film
and is dried or cured to form a film. Examples of film deposition
include physical growth methods such as vapor deposition, ion
plating and sputtering; and chemical vapor growth methods such as
plasma CVD and catalytic CVD under reduced pressure, and CVD under
an atmospheric pressure. Among these, sputtering is particularly
preferable because it can provide a dense film at a low
temperature.
When a film formed on a matrix base 120 is UV-ray curable, a base
film detailed in Embodiment 2 can be used because transparency is
required. Furthermore, light transmittable resins can be used,
including polyethylene resins, polypropylene resins, polyester
resins, ethylene vinyl copolymer resins, polyvinyl chloride resins,
cellulose resins, polyamide resins, polyimide resins, polycarbonate
resins, polystyrene resins and vinyl acetate resins.
When it is necessary to protect a film from moisture or UV rays, it
is preferable not only to form a gas barrier layer on a supporting
substrate 120 but also to laminate a cover film made of a resin
exhibiting good water proof. Examples of such a resin include
polyethylene, polypropylene, polyvinyl alcohol, cellulose,
polycarbonates, polyesters, acrylic compounds, polyether sulfones,
polyamides, polyimides and polyolefins. Among these, preferred are
celluloses such as triacetylcellulose; polyesters such as
polycarbonates and polyethylene terephthalate; and acrylic
compounds.
A cover film is desirably selected from those which are chemically
and thermally stable and easily peelable from a thin film layer.
Specifically, preferred are thin sheet films with good surface
flatness including polyesters, polyethylene, polypropylene,
polyethylene terephthalate and polyvinyl alcohol. A mold-released
film for endowing with peelability may be used.
Furthermore, forming a gas barrier layer on a cover film is
effective. The gas barrier layer can be formed on both sides or one
side of the cover film. When the gas barrier layer is formed on one
side of the cover film, it is effective that it is formed on a side
contacting with a matrix base 120 in the cover film.
There will be more specifically described a process for forming a
functional device layer or an optically functional layer on a base
film with reference to FIG. 3. FIG. 3 is a conceptual view
illustrating a partial manufacturing step in a manufacturing
process for an organic EL light emitting device.
A functional film in which a reflection electrode is formed on a
base film 105 is fed from a wind-off roll to a wind-up roll. During
the functional film comprising the reflection electrode is wound-up
into a wind-up roll, a thin film made of an organic material to be
the next light-emitting layer is formed. In terms of the organic EL
layer 110, the organic EL layer 110 made of an organic material to
be a light-emitting layer is formed on the reflection electrode by
vapor deposition or application. In FIG. 3A, an application method
is illustrated. In an application method, a light-emitting layer is
formed by application, dried, cooled and then wound-up into a
wind-up roll. Since the transparent electrode is not continuously
deposited in FIG. 3A, it is wound-up into the wind-up roll after
laminating the cover film 111 on the organic EL layer 110 by
lamination.
A cover film is desirably selected from those which are chemically
and thermally stable and easily peelable from a thin film layer.
Specifically, preferred are thin sheet films with good surface
flatness including polyesters, polyethylene, polypropylene,
polyethylene terephthalate and polyvinyl alcohol. A mold-released
film for endowing with peelability may be used.
In the functional film comprising the organic EL layer 110, a
transparent electrode is then formed on an organic EL layer 110 by
vacuum deposition or sputtering, to provide an organic EL light
emitting device. As in forming the organic EL layer 110, a cover
film 111 is formed on a transparent electrode and wound-up by a
winding-up roller. There will be described a method for laminating
a polarizing film and a retardation film on the functional film
comprising the organic EL light emitting device with reference to
FIG. 3(b).
The functional film comprising the organic EL light emitting device
is fed from a winding-off roll, a cover film on the functional film
is peeled, and then a polarizing film is laminated on a functional
thin film layer (transparent electrode) 112 on the functional film
by lamination. In the functional film in which a polarizing film
113 is formed on a supporting film 115 and a cover film 111 is
laminated on the polarizing film 113, a cover film 111 is peeled,
and then a polarizing film 113 is laminated by a lamination method,
on a functional thin film layer (transparent electrode) 112 on the
functional film using a transfer roller via the supporting film
115. Next, the supporting film 115 is peeled, the polarizing film
113 is exposed, and a retardation film 116 is laminated on the
polarizing film 113 by a lamination method.
The retardation film 116 is, after peeling the supporting film 115,
transferred on the polarizing film 113 via the cover film 111 by a
transfer roller.
When it is transferred via a transfer roller by lamination, it may
be directly transferred on the functional thin film 112 using the
transfer roller, but transfer via a film is more preferable because
dust or damage is prevented in the functional thin film 112, the
transferred polarizing film 113 and the retardation film 116.
For preventing a roller from damaging a functional thin film during
transfer, the cover film is preferably an excoriation-resistant
protective film. Preferable examples of an excoriation-resistant
material include polyester resins and polyethylene resins.
For a functional film where a functional thin film is formed
between a supporting film and a cover film, either the supporting
film or the cover film can be peeled first.
Transfer via a transfer roller may be conducted by an appropriate
method such as compression, thermocompression and adhesive methods,
which is selected depending on a design.
Although the retardation film 116 is continuously transferred after
transferring the polarizing film 113 in FIG. 3B, only the
polarizing film 113 may be transferred by a roll-to-roll process
and then the retardation film 116 may be transferred in a similar
manner as shown in FIG. 3A.
After transferring the retardation film 116, the cover film 111 may
be laminated on the retardation film 116 as shown in FIG. 3A (not
shown).
In order to facilitate transfer and peeling, a peel layer may be
placed between the film and the thin film. In FIG. 3, there is
shown only one transfer roller, but a flat table or roller may be
placed in the opposite surface via the film in the transfer roller.
In a roll-to-roll process, pressing by a pair of rollers, rather
than a flat table, is preferable because the film is not
damaged.
In order to improve adhesiveness between the cover film and the
functional thin film, an adhesion layer may be formed in the cover
film. It is preferable that the adhesion layer is substantially
adhesive when the cover film is laminated with the functional thin
film layer, while it can be easily peeled during peeling. For
example, an adhesive whose adhesive power is reduced by UV rays or
heating is preferable.
There will be described a process for manufacturing a
liquid-crystal panel equipped with a backlight with reference to
the conceptual view of FIG. 4.
A barrier layer is formed on a thin film consisting of a first
organic film as a base film. The barrier layer is formed for
preventing interaction between a material used later and the base
film material. For the purpose of this, an inorganic material such
as SiO.sub.2 and SiON is suitable. Next, for a retardation
function, an optically anisotropic material such as a polymerizable
liquid crystal is applied to a film substrate to form a retardation
layer. Then, a layer having a polarizing function is formed on the
retardation layer. The step is conducted by, for example,
laminating a separately formed thin film having a polarizing
function on a film substrate. Then, to the film substrate is
transferred a circuit consisting of a thin-film transistor formed
on a glass substrate by a conventional method, to form a TFT
circuit layer. Finally, a color filter (CF)/black matrix (BM) and a
spacer which have been formed on a dry film are transferred in one
process, to form a color filter layer. Thus, a first functional
film is provided. The color filter layer may be formed by applying
a color filter material to a film substrate by an ink-jet
process.
Next, there will be described a manufacturing process for a
backlight. On a base film are formed a reflection electrode and
then an organic EL layer. The organic EL layer is formed by vapor
deposition when the organic EL material is a low molecular-weight
material and an application process by an ink-jet method when the
material is a high molecular-weight material. Then, a transparent
electrode made of an electrically conductive transparent material
to be an upper electrode in an organic EL layer is formed to
provide an organic EL device layer to be a light source in a
backlight. Next, on the upper surface of the organic EL device
layer is formed a barrier layer as a protective layer. Then, a
retardation layer and a polarizing layer are formed as described
for the first functional film. Finally, a transparent electrode to
be an upper electrode in a liquid crystal device is formed over the
whole surface to provide a second functional film.
Finally, a first functional film and a second functional film are
cut from the roll. Then, each film is oriented, a sealing material
is applied and attached to the periphery of the display area, a
liquid crystal is injected and the injection port is sealed to give
an active matrix liquid-crystal panel with a backlight.
An active matrix liquid-crystal panel with a backlight may be
prepared by orienting the first functional film and the second
functional film, applying a sealing material to the periphery of
the display area, laminating and cutting the first functional film
and the second functional film, injecting a liquid crystal and
sealing the injection port. In this process, the functional thin
film surfaces 105 of the first functional film and the second
functional film are faced each other and are laminated such that
the longitudinal directions of these functional film are orthogonal
to each other. Thus, alignment during lamination can be facilitated
(see FIG. 5C).
In this embodiment, the film is wounded from a roll to a roll while
the functional thin film 112 is formed. If the roll for feeding is
in contact with the functional thin film 112 formed on the base
film 105, the roll is in contact with the surface of the functional
thin film 112, leading to attachment of dusts on the surface of the
functional thin film 112. As shown in FIGS. 5A and B, an optically
functional layer or a functional device layer is preferably formed
on the base film 105 while being separated from the edge orthogonal
to the feeding direction of the base film. Since the base film 105
is fed while a functional device is formed on it, it must be
designed to prevent bending in the surface of the base film. A
distance from the edge is determined depending on the shape of the
feeding roll, and the edge of the base film 105 may be
perforated.
Each functional film described in the embodiment may be carried to
the next process or stored while being wound-up as a roll.
When the functional film of this embodiment is wounded-up as a
roll, the operation of each process is finished. The wound-up roll
is conveniently carried and stored, as well as needs a narrower
space in comparison with a conventional manufacturing process using
a substrate.
There will be described a base film made of an organic resin as
Embodiment 2 of this invention.
A base film as a supporting substrate for forming a liquid crystal
display panel is required to be a plastic material which is thin,
highly heat-resistant, transparent to a light, particularly to a
light in the visible region and optically isotropic, i.e., having a
small phase difference. It may be used as, in addition to a
supporting substrate for forming a liquid-crystal panel, a
supporting film for a functional thin film.
Furthermore, in terms of flexibility, it desirably has a curvature
radius, r=40 mm or less as a measure of bending resistance. When r
is at least 40 mm, a roll having a minimum diameter of .phi.=100 mm
which is used in a roll-to-roll process can be used. In addition, a
liquid-crystal panel or a liquid crystal display comprising a
highly flexible supporting substrate is resistant to falling impact
because it can absorb the impact by bending. When r is 20 mm or
more, breakage or wrinkling of the film can be prevented.
When a thin-shaped display device such as an electronic book is
manufactured, feeling of a conventional paperback such as a pocket
edition can be maintained.
When being mounted as a display device in an apparatus for a mobile
application, it is essential that it is resistant to an impact and
falling. In a conventional glass substrate, shock resistance is
dependent on a part receiving a falling impact because of its
material properties, and thus an impact to an edge may readily
break the substrate. On the other hand, a plastic substrate
exhibits a higher shock resistance than a glass, but when it
receives an impact on an edge, the supporting substrate and a
transistor or interconnection mounted on the supporting substrate
are directly exposed to the impact as is in a glass substrate.
Reducing a weight of a liquid-crystal panel by improving
flexibility of the supporting substrate and thinning the supporting
substrate in the liquid crystal display panel may improve shock
resistance owing to weight reduction.
In terms of a thickness, there are no particular restrictions to an
upper limit when the substrate is used only in a roll-to-roll
process. However, in the light of size reduction and weight
reduction of the overall display device, the substrate is
preferably thinner than 400 .mu.m for a glass substrate, more
preferably thinner than 200 .mu.m for a plastic substrate. For
meeting the requirements of size reduction and weight reduction in
the overall display device, the thickness is preferably 10 .mu.m to
150 .mu.m, more preferably 10 .mu.m to 100 .mu.m. When it is 10
.mu.m or more, wrinkling or breakage during carrying can be
prevented.
In terms of heat resistance, the substrate is required to resistant
to optical and mechanical distortion at a temperature when a
functional film is formed. For the purpose of this, mechanical and
optical variation is preferably at least 5% or less to a
temperature history at 200.degree. C., more preferably 5% or less
to a temperature history at 250.degree. C.
The term "optical variation" refers to deterioration in optical
transparency and increase in a phase difference due to temperature
variation and the term "mechanical variation" refers to
deterioration in flexibility and variation in a dimension.
In terms of transparency, the substrate is required to be
transparent in the visible range (380 nm to 800 nm). It exhibits
higher transparency at least in the range of 450 nm to 700 nm, more
preferably 400 nm to 700 nm, further preferably 380 nm to 800 nm
(the visible range). When it exhibits higher transparency in the
range of 450 nm to 700 nm, it is practically acceptable.
Transparency in the range of 400 nm to 700 nm is more preferable
and may be substantially adequate even for a case where the
strictest hue is needed, but further preferably, it exhibits a high
light transmittance in the overall visible range of 380 nm to 800
nm. A wider wavelength range exhibiting transparency may result in
an image display device capable of more precisely reproducing an
original color. It is substantially acceptable that to a desired
thickness of the base film, a light transmittance (wavelength; 550
nm) is 80% or more, more preferably 85% or more, further preferably
90% or more.
It is necessary that a phase difference (wavelength; 550 nm) to a
thickness of the base film is negligible to a 1/4.lamda.,
1/2.lamda. retardation film. Generally, at a wavelength of 500 nm
within the visible range, a value in a normal line direction in the
plane of the base film is preferably 10% or less (about 10 nm or
less), more preferably 5% or less (about 5 nm or less) of
1/4.lamda.. Here, 10 nm or less of a phase difference (wavelength;
550 nm) is acceptable.
When the base film has retarding function, 1/4.lamda. and
1/2.lamda. values may be used.
Examples of a plastic material for a base film in terms of heat
resistance include acrylic resins, epoxy resins, cyclic olefin
resins, polyimides and polyamides. Meanwhile, in terms of higher
transparency and optical isotropy, an acrylic resin or a cyclic
olefin resin may be preferably used.
Since a base film must show minimum dimensional change during a
process for manufacturing a display, a coefficient of thermal
expansion is preferably 50 ppm/.degree. C. or less. A coefficient
of thermal expansion of a plastic material can be reduced by adding
inorganic fillers. Inorganic fillers must be smaller than a
wavelength of the visible light for maintaining transparency of the
film, and a particle size of 380 nm or less is practically
acceptable although transparency may be deteriorated around at the
shortest wavelength of the visible light. More preferably a size of
1 to 100 nm can be used without deterioration in transparency in
the overall visible range. Although a size of 1 nm or less may be
acceptable, it is difficult to prepare fillers with a size of 1 nm
or less by current technique.
When a base film is used as a supporting film in an optically
functional thin film, it may be cured by UV rays. In such a case,
the base film preferably exhibits a higher transmittance to UV
rays. Thus, a particle size of inorganic fillers is preferably 1 nm
to 200 nm, more preferably 1 nm to 200 nm. Although a size of 1 nm
or less may be acceptable, it is difficult to prepare fillers with
a size of 1 nm or less by current technique.
The amount of the inorganic fillers is preferably 5% by weight to
90% by weight both inclusive, more preferably 10% by weight to 50%
by weight both inclusive. When it is 5% by weight or more, a
coefficient of thermal expansion can be reduced and when it is 90%
by weight or less, the substrate is resistant to breakage.
Examples of the inorganic fillers include titanium dioxide, zinc
oxide, alumina and silicon oxide. The inorganic fillers can be
incorporated, for example, by dispersing dry powdery silicon oxide
particles using a mixer having higher dispersing ability; by
blending a colloid (sol) dispersed in an organic solvent and other
components and removing the organic solvent in vacuo optionally
with stirring; or by blending a colloid (sol) dispersed in an
organic solvent and other components, removing the solvent as
necessary and then further removing the solvent by flow casting. An
example of an apparatus having higher dispersing ability is a bead
mill.
Since the base film of Embodiment 2 is a thin film made of an
organic resin, common air components such as oxygen and moisture
enters a liquid crystal layer and an organic EL layer. It may lead
to adverse influence such as bubble generation and deterioration in
a specific resistance in a liquid crystal device and forming of a
non-emitting part in an emitting area in an organic EL device.
Therefore, a gas barrier layer may be formed either one or both
surfaces of the base film for preventing the air from entering.
When it is formed in one surface of the base film, it may be
effective on either side, but it may be more effective when being
formed on the surface on which a functional thin film is to be
formed.
A gas barrier layer must be transparent because the substrate must
transmit a light. Thus, examples of a material of the gas barrier
layer include organic materials such as polyvinyl alcohols and
polyvinylidene chlorides; organic-inorganic composite materials
such as those of an organic material with an inorganic material
including a clay mineral (an amorphous clay mineral such as
Al.sub.2O.sub.3-2SiO.sub.2(5H.sub.2O and
Al.sub.2O.sub.3SiO.sub.22-3H.sub.2O, or a crystalline clay mineral
such as (Si,Al)O.sub.4 tetrahedral sheet and (Al,Mg)(O,OH).sub.6
octahedral sheet); and a thin film of an inorganic material such as
silicon oxide and aluminum oxide. A film thickness may be more
reduced by using an inorganic material because it exhibits good gas
barrier properties under a high humidity atmosphere and is
effective with a smaller thickness. Furthermore, two or more of
these layers may be laminated.
An organic material may reduce a cost because a gas barrier film
can be in the form of a coating or laminated film in contrast to an
inorganic material. It is inevitably inferior to a gas barrier film
made of an inorganic material in terms of temperature dependency
and moisture resistance. Thus, the organic material is desirably
disposed in the surface facing the outside light in the
liquid-crystal panel.
A thickness of a gas barrier layer is preferably 1 .mu.m to 10
.mu.m when it is made of an organic material or an
organic-inorganic composite material and preferably 10 nm to 1
.mu.m when it is made of an inorganic material. When it is made of
an organic material or an organic-inorganic composite material, a
thickness of 1 .mu.m or more can adequately prevent common air
components such as oxygen and moisture from entering a liquid
crystal layer or an organic EL layer. A thickness of 10 .mu.m or
less does not influence properties of the base film such as an
expansion coefficient.
When it is made of an inorganic material, a thickness of 10 nm or
more can adequately prevent common air components such as oxygen
and moisture from entering a liquid crystal layer or an organic EL
layer, while a thickness of 1 .mu.m or less can prevent breakage
during bending.
A gas barrier layer can be formed on a film by an application
method for an organic material or an organic-inorganic composite
material and by any of various film deposition methods for an
inorganic material. In an application method, a liquid such as a
liquid organic material or a solution thereof is applied on a film
and is dried or cured to form a film. Examples of film deposition
include physical growth methods such as vapor deposition, ion
plating and sputtering; and chemical vapor growth methods such as
plasma CVD and catalytic CVD under reduced pressure, and CVD under
an atmospheric pressure. Among these, sputtering is particularly
preferable because it can provide a dense film at a low
temperature.
Although there has been described a base film which is thin, heat
resistant, transparent to a light, particularly a visible light and
optically isotropic, i.e., having a small phase difference (optical
lag) as Embodiment 2, an optically anisotropic film can be
used.
A base film may have retarding function and/or polarizing
function.
For example, when a phase difference in the base film is .lamda./2,
.lamda./4, it is not necessary to endow the base film with
retarding function later. When the film has polarizing function, it
is not necessary to endow the base film with polarizing function
later.
Furthermore, when endowing the base film with light-emitting
function, it can have a structure where a light does not pass
through the base film as described later. In such a case, the base
film is not necessarily light-transmissive, and thus the base film
itself may have gas barrier function.
There will be described a manufacturing process where a peripheral
functional circuit and a thin-film transistor for driving a pixel
are transferred on a base film as Embodiment 3 of this
invention.
In order to reduce the number of components, narrow a frame and
reduce power consumption in a liquid crystal display, it is
essential to integrate, on a substrate, a DA converter, a liquid
crystal driving circuit and so forth, which have been
conventionally external parts. Therefore, transistor performance of
a thin-film transistor for driving a pixel cannot be deteriorated.
Thus, in this embodiment, a thin-film transistor is formed on a
glass substrate by a conventional process, the glass substrate is
removed, and then the thin-film transistor formed on the glass
substrate is transferred to a base film.
A polysilicon thin-film transistor may be prepared by either a
high-temperature process or low-temperature process. In a
high-temperature process, a glass substrate resistant to
high-temperature such as a quartz substrate or fused quartz
substrate must be used. Since a quartz substrate or fused quartz
substrate may lead to problems such as difficulty/much time in
etching off, a low-temperature process in which a common glass
substrate can be used is preferable.
When etching off the glass substrate, it is necessary to prevent
damage on the transistor by forming a barrier film on the glass
substrate for stopping etching and a protective film on the surface
of the transistor. The barrier film preferably gives a low etching
rate to a glass etchant, and is desirably a nitride or oxynitride
film.
The protective film must be made of a material resistant to a
strong acid such as hydrofluoric acid. During etching, a
temperature of the etchant must be kept constant for uniform
etching.
There will be described a retardation film in Embodiment 4. The
retardation film may be an application type retardation film or
lamination type retardation film. First, an application type
retardation film will be described.
An application type retardation film is formed by applying a
polymerizable liquid crystal composition containing a liquid
crystal compound having a polymerizable group on a support by a
common application method to give a liquid crystal thin film. The
surface which is not in contact with the substrate in the liquid
crystal thin film is preferably in contact with the dust-removed
dry air or an inert gas such as nitrogen, more preferably an inert
gas such as nitrogen. Then, the polymerizable liquid crystal
composition is oriented at a temperature within a range where a
liquid crystal phase is formed, and then was polymerized to give a
solid thin film. A film thickness and a birefringence of the
retardation film are selected, depending on phase control
properties required for a liquid crystal display panel.
Since the polymerizable liquid crystal composition is directly
applied to the support, an application type retardation film may
have a significantly reduced film thickness (e.g., 100 .mu.m or
less) in comparison with a lamination type retardation film. An
application type retardation film has a film thickness of
preferably 0.1 .mu.m to 30 .mu.m, more preferably 0.3 to 15 .mu.m,
further preferably 0.5 .mu.m to 10 .mu.m. A birefringence may
generally vary within a range of 0.0 to 0.5 as a composition of the
polymerizable liquid crystal composition varies. A film thickness
and a birefringence can be determined, depending on a required
retardation as in a 1/2 wavelength plate or a 1/4 wavelength plate
and convenient manufacturing conditions.
Next, there will be described a material for an application type
retardation film.
A polymerizable liquid crystal compound used in this embodiment may
be any compound which can be applied to a plastic sheet and can be
oriented utilizing its liquid crystal state, but it must be a
compound in which a temperature range where thermal polymerization
of the polymerizable group is not initiated is at least partially
contained in a temperature range where the compound is in a liquid
crystal state. Furthermore, it must be able to be applied and
oriented within the temperature range. A film having
phase-difference controlling function in this invention preferably
has a thickness as small as possible. In other words, a film having
a higher birefringence is preferable. Specifically, a composition
containing the following compound may be shown as an example.
A polymerizable liquid crystal composition where a monofunctional
acrylate or methacrylate is represented by formula (1):
##STR00001##
wherein X represents hydrogen or methyl; 6-membered rings A, B and
C independently represent
##STR00002##
wherein n represents an integer of 0 or 1; m represents an integer
of 1 to 4; Y.sub.1 and Y.sub.2 independently represent a single
bond, --CH.sub.2CH.sub.2--, --CH.sub.2O--, --OCH.sub.2--, --COO--,
--OCO--, --C(C--, --CH.dbd.CH--, --CF.dbd.CF--,
--(CH.sub.2).sub.4--, --CH2CH2CH2O--,
--OCH.sub.2CH.sub.2CH.sub.2--, --CH.dbd.CHCH.sub.2CH.sub.2-- or
--CH.sub.2CH.sub.2CH.dbd.CH--; Y.sub.3 represents hydrogen,
halogen, cyano, alkyl having 1 to 20 carbon atoms, alkoxy, alkenyl
or alkenyloxy.
Next, there will be more specifically described a process for
manufacturing an application type retardation film.
An application type retardation film is prepared by forming an
oriented film on a transparent support, rubbing the film as
necessary, applying a layer containing a polymerizable liquid
crystal on the film, drying it by removing an unnecessary solvent,
orienting the liquid crystal and decomposing a preliminarily added
photo- or thermal-polymerization initiator by UV irradiation or
heating to initiate polymerization of the liquid crystal. If
necessary, a protective layer may be applied on the film.
The polymerizable liquid crystal is preferably dissolved in an
appropriate solvent before application. Although the type of a
solvent or a concentration cannot be generally determined because a
liquid crystal has a different property depending on its structure,
a solvent in which the liquid crystal is dissolved in a higher
solubility is preferable in the light of providing a homogeneous
thin film, preferably including halogen compounds such as
dichloromethane and chloroform; ketones such as acetone and methyl
ethyl ketone; esters such as ethyl acetate; amides such as
dimethylacetamide, dimethylformamide and N-methyl-pyrrolidone; and
alcohols such as isopropanol and perfluoropropanol.
It is well known in a liquid crystal that an oriented film may
often give significant influence on molecular orientation during
forming a liquid crystal phase, and an inorganic or organic
oriented film is used. Although there may be a combination of a
liquid crystal and a support in which an effective orientation may
be obtained only by rubbing the support surface and then applying
the combination on it, the most universal method involves the use
of an oriented film.
Typical examples of an oriented film formed on a support include an
SiO evaporated film as an inorganic rhombic evaporated film and a
polyimide film in which an organic polymer film has been
rubbed.
A typical example of an organic oriented film is a polyimide film.
In this film, a polyamic acid (for example, AL-1254 (JSR
Corporation), SE-7210 (Nissan Chemical Industries, Ltd.)) can be
applied on a support surface, fired at a temperature of 100.degree.
C. to 300.degree. C. and then rubbed to orient the liquid crystal.
A coating film of alkyl-chain modified Poval (for example, MP203,
R1130 (both from Kuraray Co., Ltd.)) can be endowed with the
orienting ability only by rubbing without firing. In addition, most
of organic polymer films giving a hydrophobic surface such as
polyvinylbutyral and polymethyl methacrylate may be endowed with a
liquid crystal orienting ability only by rubbing the surface.
A typical inorganic rhombic evaporated film is an SiO rhombic
evaporated film. It is prepared by colliding SiO vaporized
particles on a support surface from an oblique direction in a
vacuum chamber to form an oblique evaporated film with a thickness
of about 20 to 200 nm as an oriented film. With the evaporated
film, when the liquid crystal is oriented, an optical axis of the
liquid crystal layer is oriented to a particular direction on a
plane perpendicular to the support surface including the track of
SiO vapor-deposited particles.
It is also advantageous in that when using a silicon oxide (SiO)
rhombic evaporated film as an oriented film, a gas barrier film in
the base film as described in Embodiment 2 can be used. Here,
silicon oxide is desirably SiO.sub.x (x=1.6 to 1.9).
In addition to the above method, a polymerizable liquid crystal
applied on a support may be also oriented by magnetic-field or
electric-field orientation. In this method, after applying on a
support, a liquid crystal compound may be oriented to an oblique
direction, using a magnetic or electric field from a desired
angle.
In the manufacturing process for a retardation film, a common
application method may be employed. Specifically, it may be formed
as a liquid crystal thin film on a support by an application step
using an appropriate method such as flexographic printing, gravure
printing, dip coating, curtain coating and extrusion coating and
then a drying step.
Next, there will be described a lamination type retardation film
according to another form of this embodiment.
A lamination type retardation film is prepared by laminating a
pre-formed retardation film with a base film via an agglutinant or
adhesive.
It is preferable in this embodiment to use an aromatic polyamide or
aromatic polyimide because a film can been thinned more than ever
while maintaining dimensional stability required during
manufacturing an LCD. Thus, a thickness of a retarding function
layer may be reduced to several microns.
As a result, a thin film can be more thinned than a conventional
film such as polycarbonate resin films, polyether sulfone resin
films, polysulfone resin films, cyclic polyolefin resin films,
cellulose resin films and acrylic resin films having a thickness of
60 .mu.m or more for obtaining a required phase difference and
self-supporting ability.
A preferable aromatic polyamide a repeating unit represented by,
for example, formula (2) and/or formula. (3) in 50 mol % or more,
more preferably 70 mol % or more.
In the light of rigidity and heat resistance of the film, the
repeating unit is contained preferably in 50 mol % or more, more
preferably in 70 mol % or more;
##STR00003##
wherein Ar.sub.1, Ar.sub.2 and Ar.sub.3 may be selected from, for
example,
##STR00004## and fluorene residue; and X and Y may be selected
from, but not limited to, --O--, --CH.sub.2--, --CO--,
--SO.sub.2--, --S--, --C(CH.sub.3).sub.2--, --CF2-- and
--C(CF.sub.3).sub.2--.
It may be selected from those in which one or more hydrogens on the
aromatic ring are replaced by a substituent including halogen such
as fluorine, chlorine and bromine; nitro; alkyl such as methyl,
ethyl and propyl; alkoxy such as methoxy, ethoxy, propoxy and
isopropoxy; hydroxyl; and trifluoromethyl, and those in which
hydrogen in an amide bond constituting the polymer is replaced by
another substituent.
In the light of film properties, preferred is a polymer in which a
moiety having the para-oriented aromatic rings, i.e., those in
which bivalent bonds are connected coaxially or in parallel,
accounts for 50 mol % or more, preferably 75 mol % or more of the
total aromatic rings because such a film can exhibit higher
rigidity and heat resistance.
In the light of film properties, preferred is a polymer in which a
moiety having the para-oriented aromatic rings, i.e., those in
which bivalent bonds are connected coaxially or in parallel,
accounts for 50 mol % or more, preferably 75 mol % or more of the
total aromatic rings because such a film can exhibit higher
rigidity and heat resistance. Examples of two aromatic rings having
para-orientation are shown in formula (7):
##STR00005##
An aromatic polyamide used in this invention preferably contains
the repeating unit represented by general formula (2) and/or
general formula (3) in 50 mol % or more. When the content is less
than 50 mol %, another repeating unit may be introduced by
copolymerization or blending.
A retardation film used in this invention preferably has a
thickness of 1 .mu.m to 50 .mu.m for thinning a display. When the
thickness is 1 .mu.m or more, the aromatic polyamide film is highly
rigid and heat resistant, so that deterioration in flatness or
increase in a phase difference spot due to heating during its use
can be avoided. When the thickness is 50 .mu.m or less, a light
transmittance is not reduced. The thickness is preferably 2 .mu.m
to 30 .mu.m, more preferably 2 .mu.m to 15 .mu.m, further
preferably 3 .mu.m to 10 .mu.m, most preferably 3 .mu.m to 8
.mu.m.
Next, there will be an aromatic polyimide. An aromatic polyimide
according to this embodiment contains at least one aromatic ring
and at least one imide ring in a polymer repeating unit, and
preferably contains a repeating unit represented by formula (8)
and/or formula (9) in 50 mol % or more, more preferably 70 mol % or
more.
##STR00006##
##STR00007##
wherein Ar.sup.4 and Ar.sup.6 contain at least one aromatic ring;
and two carbonyl groups forming an imide ring are bound to the
adjacent carbon atom on the aromatic ring. Ar.sup.4 is derived from
an aromatic tetracarboxylic acid or its anhydride. Typical examples
are as follows:
##STR00008##
wherein Z is selected from, but not limited to, --O--,
--CH.sub.2--, --CO--, --SO.sub.2--, --S-- and
--C(CH.sub.3).sub.2--.
Ar.sup.6 is derived from a carboxylic anhydride or its halide.
Examples of Ar.sup.5 and Ar.sup.7 include, but not limited, to:
##STR00009##
wherein X and Y are selected from, but not limited to, --O--,
--CH.sub.2--, --CO--, --SO.sub.2--, --S-- and
--C(CH.sub.3).sub.2--.
It may be selected from those in which one or more hydrogens on the
aromatic ring are replaced by a substituent including halogen (in
particular, chlorine); nitro; alkyl having 1 to 3 carbon atoms (in
particular, methyl); and alkoxy having 1 to 3 carbon atoms, and,
when an amide bond is contained in the polymer, those in which
hydrogen in the amide bond is replaced by another substituent.
An aromatic polyimide in this invention contains the repeating unit
represented by formula (8) and/or (9) in 50 mol % or more, and when
the content is less than 50 mol %, another repeating unit may be
introduced by copolymerization or blending. The retardation film in
this invention has a phase difference of 50 to 3,000 nm, preferably
60 to 500 nm, more preferably 60 to 380 nm, further preferably 80
to 280 nm at a wavelength of 550 nm.
A phase difference in a film must be appropriately designed
depending on its application (e.g., 1/2.lamda. plate, 1/4.lamda.
plate). However, with a phase difference within the above range, a
film exhibiting excellent optical properties and processability can
be prepared even when the film is thinned using an aromatic
polyamide or aromatic polyimide.
It can be of course understood that a thickness of the retardation
film can be reduced by endowing the base film to be laminated with
the retarding function.
In the retardation film in this embodiment, it is preferable that a
dimensional variation in a lag axis direction and a direction
perpendicular to the lag axis direction at 150.degree. C. is 2% or
less, more preferably 1.5% or less, further preferably 1% or less,
most preferably 0% because wrinkles can be prevented during
processing such as lamination and variation in optical properties
can be minimized due to variation in a tensile under heating.
The term "lag axis" as used herein refers to a direction in a plane
in which a phase difference is maximum. In a retardation film, it
is generally a direction in which a draw ratio is maximum.
The retardation film in this embodiment can have a large
birefringence without partial deterioration in color tone in a
liquid crystal display even when it is exposed to an extreme
temperature or external force during processing because a phase
difference varies by a photoelastic effect. Furthermore, since the
film has a large photoelastic coefficient, it can be thinned. In
addition, since it exhibits good heat resistance and rigidity, it
may not be distorted even under an high-temperature or a high
tension.
For preventing tone variation in a liquid crystal display (LCD), a
light transmittance at any wavelength within the range of 450 nm to
700 nm is preferably 80% or more, more preferably 85% or more,
further preferably 90% or more.
Furthermore, in a film of this invention, a light transmittance at
400 nm is preferably 65% or more, more preferably 75% or more, most
preferably 90% or more. When a light transmittance at 400 nm is 65%
or more, transparency can be further improved.
It is preferable that the film of this embodiment has a Young's
modulus of 4 GPa or more in at least one direction as determined in
accordance with JIS-C2318 because it can be resistant to a force
applied during processing or its use and flatness can be further
improved. The film can be thinned when a Young's modulus in at
least one direction is 4 GPa or more.
If a Young's modulus in any direction is less than 4 GPa,
deformation may occur during processing. Although there is not a
particular upper limit to a Young's modulus, a Young's modulus of
more than 20 GPa may lead to deterioration in film toughness and
thus to difficulty in film deposition or processing. A Young's
modulus is more preferably 8 GPa or more, further preferably 10 GPa
or more.
In the film of embodiment, a coefficient of thermal expansion from
80.degree. C. to 120.degree. C. is preferably 50 to 0 ppm/.degree.
C. A coefficient of thermal expansion is measured in the course of
cooling after warming to 150.degree. C. using TMA. Assuming that an
initial sample length at 25.degree. C. and 75 RH % is L0, a sample
length at a temperature of T1 is L1 and a sample length at a
temperature of T2 is L2, a coefficient of thermal expansion from T1
to T2 can be determined by the following equation. Coefficient of
thermal expansion (ppm/.degree.
C.)=((L2-L1)/L0)/(T2/T1).times.10.sup.6
A coefficient of thermal expansion is more preferably 30 to 0
ppm/.degree. C., further preferably 20 to 0 ppm/.degree. C. In the
film of this embodiment, a coefficient of humidity expansion at
25.degree. C. and from 30% RH to 80% RH is preferably 200 to 0
ppm/% RH. A film sample with a width of 1 cm and a length of 15 cm
is fixed in a high-temperature and high-humidity chamber, the
atmosphere is dehumidified to a certain humidity (about 30% RH),
and after the film length becomes constant, it is humidified (about
80% RH) to extend by moisture absorption. After 24 hours, moisture
absorption comes to equilibrium and film extension also comes to
equilibrium. From the extended length observed, a coefficient of
humidity expansion is calculated in accordance with the following
equation. Coefficient of humidity expansion ((cm/cm) % RH)=extended
length/(sample length.times.humidity difference)
A coefficient of humidity expansion is more preferably 100 to 0 ppm
% RH, further preferably 30 to 0 ppm % RH. A small coefficient of
thermal expansion and a small coefficient of humidity expansion may
result in reduction in environmental dimensional variation and thus
less variation in optical properties such as a phase
difference.
The film of this embodiment may be used in one sheet as a
retardation film, or alternatively may be laminated with the same
or different type of retardation film.
There will be described an example of manufacturing an aromatic
polyamide film.
An aromatic polyamide can be prepared by various methods such as
low-temperature solution polymerization, interfacial
polymerization, melt polymerization and solid-phase polymerization.
When being prepared by low-temperature solution polymerization,
i.e., from a carboxylic dichloride and a diamine, the synthesis is
conducted in an aprotic organic polar solvent.
Examples of a carboxylic dichloride include terephthalic
dichloride, 2-chloro-terephthalic dichloride, isophthalic
dichloride, naphthalenedicarbonyldichloride,
biphenyidicarbonylchloride and terphenyidicarbonylchloride. For
preparing the aromatic polyamide film of this embodiment,
2-chloro-terephthalic dichloride or terephthalic dichloride is
used.
When using an acid dichloride and an diamine as monomers, an
aromatic polyamide solution obtained contains hydrogen chloride as
a byproduct, which is neutralized with a neutralizing agent
including inorganic neutralizing agents such as calcium hydroxide,
calcium carbonate and lithium carbonate; and organic neutralizing
agents such as ethylene oxide, propylene oxide, ammonia,
triethylamine, triethanolamine and diethanolamine. A reaction
between an isocyanate and a carboxylic acid is effected in the
presence of a catalyst in an aprotic organic polar solvent.
Polymerization using two or more diamines can be conducted by a
stepwise reaction procedure where to one diamine is added 10 to 99
mol % of an acid dichloride to initiate a reaction, then another
diamine and then the acid dichloride are added to initiate a
reaction, and so on, or alternatively a procedure where all the
diamines are blended and to the mixture is added an acid dichloride
to initiate a reaction. Polymerization using two or more acid
dichlorides can be similarly conducted by a stepwise or
simultaneous-addition procedure. In any case, a molar ratio of the
total diamines to the total acid dichlorides is preferably 95 to
105:105 to 95. If the ratio is outside of the range, a polymer
solution suitable for molding cannot be obtained.
Examples of an aprotic polar solvent used in manufacturing the
aromatic polyamide of this embodiment include sulfoxide solvents
such as dimethylsulfoxide and diethylsulfoxide; formamide solvents
such as N,N-dimethylformamide and N,N-diethylformamide; acetamide
solvents such as N,N-dimethylacetamide and N,N-diethylacetamide;
pyrrolidone solvents such as N-methyl-2-pyrrolidone and
N-vinyl-2-pyrrolidone; phenol solvents such as phenol, o-, m- or
p-cresol, xylenols, halogenated phenols and catechol;
hexamethylphoshoramide; and .gamma.-butyrolactone, which is
desirably used alone or as a mixture. Furthermore, aromatic
hydrocarbons such as xylenes and toluene can be used.
In order to accelerate dissolution of a polymer, an alkali metal or
alkaline-earth metal salt can be added to a solvent in 50% by
weight or less.
The use of an aromatic diacid chloride and an aromatic diamine as
monomers results in generation of hydrogen chloride as a byproduct,
which is neutralized with a neutralizing agent including inorganic
neutralizing agents such as calcium hydroxide, calcium carbonate
and lithium carbonate which are salts of a cation of Group I or II
in the periodic table with an anion such as hydroxide or carbonate
ion, and organic neutralizing agents such as ethylene oxide,
propylene oxide, ammonia, triethylamine, triethanolamine and
diethanolamine. Furthermore, for improving humidity properties of a
base film, to a polymerized system can be added, for example,
benzoyl chloride, phthalic anhydride, acetyl chloride or aniline to
block the ends of the polymer. A reaction between an isocyanate and
a carboxylic acid is effected in the presence of a catalyst in an
aprotic organic polar solvent.
Furthermore, the aromatic polyamide of this embodiment can contain
10% by weight or less of an inorganic or organic additive in order
to improve surface forming and processability. Although the
additive can be colorless or colored, a colorless and transparent
material is preferable in the light of avoiding deterioration in
the features of the transparent aromatic polyamide film of this
embodiment. Examples of an additive for surface forming include
inorganic particles such as SiO.sub.2, TiO.sub.2, Al.sub.2O.sub.3,
CaSO.sub.4, BaSO.sub.4, CaCO.sub.3, carbon black, carbon nanotube,
fullerene, zeolite and metal fine powder; organic particles such as
organic polymer particles including cross-linked polyvinylbenzene,
cross-linked acrylates, cross-linked polystyrene, polyester
particles, polyimide particles, polyamide particles and fluororesin
particles; and inorganic particles processed by, for example,
surface coating with any of the above polymers.
Furthermore, a dye can be added to the aromatic polyamide of this
embodiment to combine tune compensation functions. Examples of dyes
which can be suitably used include inorganic pigments such as
cobalt blue and organic dyes such as phthalocyanine.
These polymer solutions as such may be used as a film-deposition
stock solution. Alternatively, a polymer is isolated and then
dissolved in any of the above organic solvents or an inorganic
solvent such as sulfuric acid before being used as a
film-deposition stock solution.
There will be described film formation. A film-deposition stock
solution prepared as described above is used for film forming by a
so-called solution film-deposition method. Examples of a solution
film-deposition method include a dry-wet method, a dry method and a
wet method. Any of these can be used for film deposition, but
herein, a dry-wet method will be described as an example.
When a film is deposited by a dry-wet method, the stock solution is
extruded from a nozzle on a support such as a drum and an endless
belt to form a thin film. Then, the solvent is evaporated from the
thin film layer, and the thin film is dried until it becomes
self-maintaining. Drying can be conducted under the conditions of a
temperature: room temperature to 220.degree. C. and a period: up to
60 min. The smoother the surface of the drum or the endless belt
used in this drying step is, the smoother a film obtained is. The
film after the drying step is peeled from the support and
introduced to a wet step, subjected to desalting and solvent
removal, and further subjected to drawing, drying and heating to
provide a retardation film.
A draw ratio as a surface draw ratio, which is a measure of drawing
is preferably within a range of 0.8 to 8, more preferably 1.3 to 8
(a surface draw ratio is defined as a value obtained by dividing a
film area after drawing by a film area before drawing. A value of 1
or less means relaxation). Heating is preferably conducted at a
temperature of 200.degree. C. to 500.degree. C., preferably
250.degree. C. to 400.degree. C. for several seconds to several
minutes. In addition, it is effective to slowly cool a film after
drawing or heating; specifically, cooling at a rate of 50.degree.
C./sec or less is effective. The film prepared from the aromatic
polyamide of this embodiment may be a monolayer film or laminate
film.
There will be described a polarizing film as Embodiment 5 of this
invention. A polarizing film which can be preferably used as this
embodiment is prepared by forming a film as described in (1) or (2)
below and transferring only a polarizing function layer to a base
film by means of heat, pressure or an adhesive. Furthermore, it is
also useful to separately prepare a mold-releasing film to be a
matrix base for a polarizing film, forming a polarizing function
layer in a peelable state on the mold-releasing film, then
transferring only the polarizing function layer to a base film and
sticking it by, for example, heat, pressure or an adhesive.
There are two preparation methods: (1) a polarizing film
orientationally adsorbed by a polymer film in which iodine or a
dichroic dye is strongly molecular-oriented in one axis direction
and is laminated with a base film by, for example, heat, pressure,
a glue or an adhesive; and (2) a resin pellet containing iodine
and/or dichroic dye is shaped into a film by, for example, melt
extrusion or solution casting; the film is drawn to form a
polarizer in which iodine and/or a dichroic dye is strongly
oriented in one axis direction; and then the polarizer is laminated
with a base film by, for example, heat, pressure, a glue or an
adhesive.
Examples of a resin used herein include polyvinyl alcohol resins
such as polyvinyl alcohols, partially formated polyvinyl alcohols
and partially saponified ethylene-vinyl acetate copolymers;
polyester resins such as polyolefin resins, acrylic resins, PET
(polyethylene terephthalate) and PEN (polyethylene naphthalate);
polyamide resins; polyamide imide resins; polyimide resin;
polycarbonate resins; and polysulfone resins.
There will be described a color filter as Embodiment 6. A color
filter of this embodiment is any of two types, i.e., a film type
color filter and a direct drawing type filter prepared by an
ink-jet method.
There will be described first a film type color filter and then a
direct drawing type color filter.
Embodiment 6: film type color filter
For a film type color filter, on a supporting substrate are formed
black (black matrix), red, green and blue (color filter) layers. In
this embodiment, on a supporting substrate are formed these four
color filter resin layers, which are sequentially transferred on a
color filter matrix base.
These four color filter resin layers may be made of either a
photosensitive colored resin or a colored resin.
There will be described a case where a photosensitive colored resin
is used. Photosensitive colored resins to be four color filters are
deposited on separate first supporting substrates. Next, a cover
film is laminated on each photosensitive resin, which is then
wound-up. The first supporting substrate is laminated with a second
supporting substrate via the photosensitive colored resin layers.
It is then exposed from the side of the first supporting substrate
via a mask. After the exposure, the first supporting substrate is
peeled, developed and then dried.
Although depending on the type of a cross-linking agent contained
in a photosensitive resin, a drying temperature must be lower than
a temperature at which a cross-linking reaction is initiated. The
temperature is generally determined on the basis of the
pre-determined conditions before production in the light of
relationship between a cross-linking agent and a manufacturing
apparatus, but it is usually lower by 30.degree. C. to 50.degree.
C. than an initiation temperature of the cross-linking reaction.
The lower limit is determined so as to avoid an excessively longer
drying time, while the upper limit is determined such that trailing
of a lower part is avoided while an unwanted part is removed in
development.
Generally, first a black matrix is transferred to a second matrix
base for a color filter (hereinafter, referred to as "CF matrix
base") to form a black matrix layer. During transferring each color
filter to a CF matrix base, it is exposed from the side of the
first supporting substrate, developed and then dried, to form
individual colors in sequence. Thus, all of the four color filters
are transferred and formed on the CF matrix base, to provide a
color filter layer.
The color filter layer thus prepared is laminated on a functional
film comprising, for example, a thin-film transistor (hereinafter,
referred to as "TFT"), an interconnection and a pixel electrode. On
the color filter layer, there may be formed a spacer layer for
defining a distance to an opposite oriented film or a transparent
electrode.
The photosensitive resin layer is preferably weakly sticked because
it is laminated with a first supporting substrate and a cover film
and then peeled.
In addition to the photosensitive colored resin, a colored resin
may be used. In such a case, an unwanted part in the colored resin
must be etched off via a photoresist after transferring. Thus, it
must be weakly sticked during etching off while it must be firmly
sticked after drying.
Among the four color filters, chromium can be used only in the
black filter. Chromium can be deposited by physical vapor
deposition.
Next, there will be detailed a color filter prepared by an ink-jet
process as another embodiment of this embodiment.
Embodiment 6: ink-jet type color filter
An ink-jet type color filter as this embodiment is prepared by
directly drawing a colored resin consisting of a pigment on a film
by ink-jet technique. Color filter layers of black matrix, red,
green and blue can be directly drawn on a surface of a functional
film on which a color filter is to be formed. Alternatively, on a
supporting substrate is formed a color filter, which may be then
transferred to a functional film by a transfer method. A black
matrix may be prepared by depositing chromium on a supporting
substrate (the CF base as described for a film type) by physical
vapor deposition. As an example, there will be described drawing
the remaining three colors by ink-jet technique. Red, green and
blue can be simultaneously or in this sequence drawn. When drawing
red, green and blue in sequence, one color may be drawn and then
dried before drawing the next color. The order of these colors is,
of course, not limited to that in the above description.
As Embodiment 7 of this invention, there will be described an
oriented film.
A liquid-crystal panel of this invention may be assembled as
follows.
1. On a substrate cut from each of functional films A and B is
applied an optically oriented material, which after drying, is
subjected to optical orientation and polymerization to provide an
optically oriented film. Then, the surfaces having the optically
oriented film are faced each other via a spacer such that their
optical orientation directions are orthogonal. Then, after applying
a sealing material to the periphery of a display area, the
substrates are laminated, a liquid crystal is injected and the
injection port is sealed.
2. Each substrate cut from functional films A and B is subjected to
optical orientation and polymerization to form an optically
oriented film. Next, on the surfaces having the optically oriented
film is placed a sealing material to be a spacer at a desired
position, a liquid crystal is added dropwise and then the
substrates may be laminated.
3. Although the above 1, 2 are methods where a liquid crystal is
injected between the substrates cut from the functional films A and
B, a panel may be prepared by applying an optically oriented
material on a matrix base, which after drying, is then subjected to
optical orientation and polymerization to form an optically
oriented film; then transferring the optically oriented film to the
functional films A and B between which a liquid crystal is to be
sandwiched); then applying a sealing material; facing them as films
such that their optical orientation directions are orthogonal;
filling a liquid crystal as described in 1 or 2; after sealing,
cutting into the shape of the panel or alternatively after
laminating them via a sealing material, cutting into the shape of
the panel, filling a liquid crystal and then sealing the port.
In the above assembling methods 1 and 2, optical orientation
directions are not necessarily orthogonal, depending of properties
of a liquid crystal or a configuration of a liquid-crystal
panel.
An oriented film may be an optically oriented film or alternatively
an oriented film endowed with orientation by rubbing a surface of a
film on which a liquid crystal orienting agent has been applied.
First, there will be described an optically oriented film and next
a process for endowing orientation by rubbing.
Optically Oriented Film
An optically oriented film material used is an optically oriented
material containing a dichroic dye having a polymerizable group.
Here, the dichroic dye is preferably an azo dye derivative having a
polymerizable group or an anthraquinone dye derivative having a
polymerizable group. In particular, an azo dye derivative having a
polymerizable group is preferably an optically oriented material
represented by formula (4):
##STR00010##
wherein R.sup.1s are independently selected from the group
consisting of hydrogen, halogen, carboxyl, halogenated methyl,
halogenated methoxy, cyano and hydroxy; M represents hydrogen,
alkali metal or NH.sub.4; and R.sup.2 represents a polymerizable
group optionally having a linking chain.
An anthraquinone dye derivative having a polymerizable group is
preferably an optically oriented material represented by formula
(5):
##STR00011##
wherein R.sup.3s independently represent a polymerizable group, and
at least one of R.sup.3s may have a linking chain and the remaining
R.sup.3s are at least one selected from the group consisting of
hydrogen, halogen, hydroxy, nitro, sulfonic, sulfonate, halogenated
methyl, cyano, amino, formyl, carboxyl, piperidino and a radical
represented by general formula (6):
##STR00012##
wherein R.sup.4 is selected from the group consisting of hydrogen,
alkyl, cycloalkyl, phenyl, piperidino and these organic radicals
substituted with alkyl, cycloalkyl, phenyl, alkoxyl, cycloalkoxyl
or phenoxy.
Furthermore, a polymerizable group in an optically oriented
material containing a dichroic dye may be at least one selected
from the group consisting of (meth)acryloyl, (meth)acrylamide,
vinyl and vinyl ether.
On a substrate is applied one of the optically oriented material
for an optically oriented film, which is then endowed a
liquid-crystal orienting ability by irradiating it with a polarized
light. It is then heated or irradiated with a light having a
wavelength different from that used for endowing liquid-crystal
orienting ability to initiate polymerization of the polymerizable
group, giving an optically oriented film.
There will be described a process for manufacturing the optically
oriented film of this embodiment with reference to the drawings.
FIG. 6A is a conceptual view showing the step of feeding a
supporting film 150 from a wind-off roll to a wind-up roll while
during winding up the supporting film 150 into the wind-up roll, a
solution of an optically oriented material is applied on the
supporting film 150 by an appropriate method such as spin coating
and printing, dried and then subjected to optical orientation and
polymerization to provide an optically oriented film. After forming
the optically oriented film, orientation is endowed by optical
orienting. Optical orienting is a procedure of giving a liquid
crystal orienting ability by irradiating a light having such a
wavelength such that a dichroic dye derivative can be efficiently
subjected to a photoreaction; for example, visible light and UV
rays, preferably UV rays having a wavelength of around 300 to 400
nm. A film thickness is preferably 0.001 .mu.m to 1 .mu.m, more
preferably 0.005 .mu.m to 0.5 .mu.m.
A polarized light used for optical orienting may be a
linearly-polarized light or an elliptically-polarized light.
Particularly, preferred is a linearly-polarized light obtained by
filtering a light from a UV-ray source 152 such as a xenon lamp,
high-pressure mercury-vapor lamp and a metal halide lamp through a
polarized filter 153 or a polarizing prism such as a Glan-Thompson
prism and a Glan-Taylor prism. Here, for obtaining pretilt in
liquid crystal molecules, a polarized light may be irradiated from
a direction oblique to a substrate or alternatively, after
irradiation with a polarized light, a non-polarized light may be
irradiated from an oblique direction.
When using a compound having a polymerizable group for forming an
optically oriented film, change in orientation properties with time
may be prevented by polymerization. Polymerization is often
conducted generally by light irradiation such as UV rays or heating
after optical orienting. In such polymerization, a polymerization
initiator may be, as necessary, used. When polymerization is
conducted by light irradiation, it is preferable for keeping the
orientation state of the existing optically oriented material, to
use a light having, a wavelength which is not absorbed by a moiety
exhibiting anisotropic light absorption causing light orienting by
these dichroic dye molecules (for example, an azobenzene moiety in
an azo dye derivative and an anthraquinone moiety in an
anthraquinone dye derivative), i.e., a wavelength different from
that of the light for giving liquid crystal orienting ability.
Specifically, it is preferable to irradiate a non-polarized UV ray
at a wavelength of 200 to 320 nm. On the other hand, when
polymerization is conducted by heating, it is initiated by heating
a substrate on which an optically oriented material has been
applied and which has been subjected to optical orienting as
described above. A heating temperature is preferably 100.degree. C.
to 300.degree. C. both inclusive where orientation state is not
changed by optical orienting, more preferably 100.degree. C. to
200.degree. C. both inclusive.
For photopolymerization, it is preferable to use a
photopolymerization initiator as an initiator. A
photopolymerization initiator may be any known photoinitiator
without limitation; for example,
2-hydroxy-2-methyl-1-phenylpropan-1-one (Merck & Co. Inc.,
"Dalocure 1173"), 1-hydroxycyclohexyl phenyl ketone (Ciba-Geigy
Corporation, "Irgacure 184"),
1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one (Merck &
Co., Inc., "Dalocure 1116"),
2-methyl-1-[(methylthio)phenyl]-2-morpholinopropane-1 (Ciba-Geigy
Corporation, "Irgacure 907"), benzyl dimethyl ketal (Ciba-Geigy
Corporation, "Irgacure 651"), a mixture of 2,4-diethylthioxanthone
(Nippon Kayaku Co., Ltd., "KAYACURE DETX") and ethyl
p-dimethylaminobenzoate (Nippon Kayaku Co., Ltd., "KAYACURE EPA"),
a mixture of isopropylthioxanthone (Wordprekinsop Inc.,
"Cantacure-ITX") and ethyl p-dimethylaminobenzoate, acylphosphine
oxide (BASF Inc., "Lucirin TPO").
For thermal polymerization, it is preferable to use a thermal
polymerization initiator as an initiator. A thermal polymerization
initiator may be any known thermal polymerization initiator without
limitation.
Examples of a thermal polymerization initiator include peroxy
compounds such as benzoyl peroxide, 2,4-dichlorobenzoyl peroxide,
1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane,
n-butyl-4,4'-di(tert-butylperoxy) valerate and dicumyl peroxide;
azo compounds such as 7-azobisisobutyronitrile; and
tetramethylthiuram disulfide.
Although there has been described a method for forming an oriented
film on a supporting film, the above method may be applied for
preparing a film comprising an oriented film in place of a
supporting film, e.g., depositing an oriented film on a transistor
layer on a base film.
The oriented film deposited on the supporting film is transferred
on a transistor layer 155 on a base film 154. In FIG. 6, transfer
is effected by contacting the transistor layer 155 with the surface
of the oriented film which is in contact with the supporting film,
but transfer to the transfer layer 735 may be effected with the
other surface of the oriented film. For an oriented film which has
been oriented by rubbing its surface as described above, it is
preferable to use the method shown in FIG. 6 for transferring.
Transferring from a supporting film is useful in that a base film
or an organic material may not be deteriorated because a
temperature during orienting is not directly applied to the base
film or the organic material to be a light-emitting layer in an
organic EL.
Oriented Film Formed by Rubbing
As described for an optically oriented film, a liquid crystal
orienting agent is applied on a supporting film by, for example,
roll coating, spinner coating, printing, ink-jet printing. Next, a
coating film is formed by heating the applied surface. In
application of the liquid crystal orienting agent, a functional
silane or functional titanium containing compound can be
pre-applied to the surface of the substrate for further improving
adhesiveness of the coating film with the functional films A and B.
A heating temperature after application of the liquid crystal
orienting agent is a temperature equal to or lower than an
allowable temperature limit of the supporting film, preferably 80
to 230.degree. C., more preferably 100 to 200.degree. C.
A thickness of the coating film formed is preferably 0.001 .mu.m to
1 .mu.m, more preferably 0.005 .mu.m to 0.5 .mu.m.
The surface of the coating film formed is rubbed in a certain
direction with a roll which is wrapped with a cloth made of fiber
such as Nylon, Rayon and cotton. Thus, the coating film is endowed
with liquid-crystal molecule orienting ability to become a liquid
crystal oriented film.
Examples of a liquid crystal orienting agent in this invention
include, but not limited to, those containing polyamic acid and/or
polyimide.
A suitable sealing material is a photocurable resin composition
containing an urethane (meth)acrylate oligomer having two or more
urethane bonds and unsaturated bonds in one molecule, a maleimide
derivative and a silane coupling agent. Since the sealing agent
contains a particular compound, i.e., a maleimide derivative, it
has a feature that without a photopolymerization initiator, it can
be polymerized by UV rays to be a sealer for a liquid-crystal
panel, which exhibits improved long-term stability and VHR (Vapor
Hazard Ratio: obtained by dividing a saturation concentration in
the air of each substance calculated from its inherent vapor
pressure by an allowable exposure limit concentration (e.g., PEL)
for each substance, which is a hygienic safety standard for
chemical substance evaluation).
There will be detailed a backlight comprising a light-condensing
film as Embodiment 8 of this invention.
FIG. 30 shows an embodiment of a backlight comprising a
light-condensing film of this invention. This backlight comprises
an optical guide 701 comprising a light source 705 on its edge and
a light-condensing film controlling distribution of an outgoing
light angle from the light source 705. The light-condensing film is
disposed on the optical guide 701, in which an incident light from
the entrance face outgoes from the outgoing face. The
light-condensing film has flexibility indicated by a curvature
radius of 40 mm or less. In the film, light collectors 703 made of
an organic resin are arranged as an array on a light-diffusing film
704 having a coefficient of thermal expansion of 50 ppm/.degree. C.
or less. The end of the optical guide side in the light collector
array 703 is firmly sticked with the outgoing face in the optical
guide 701. In each light collector 703, the face firmly adhering to
the optical guide 701 is flat and has a smaller area than the face
in contact with the above light-diffusing film. The light collector
array may have a one-dimensional arrangement pattern or
two-dimensional arrangement pattern, but an ellipsoidal shape as
shown in FIG. 31 is preferable in the light of in-plane uniformity
of an emission brightness.
A light entering the edge of the optical guide 701 from the light
source 705 propagates within the optical guide 701 while repeating
total reflection. The propagating light enters the light-condensing
film from a contact area between the outgoing face in the optical
guide 701 and the light collector 703 in the light-condensing film.
Thus, the lights propagating within the optical guide 701
sequentially enter the light-condensing film from the contact area,
and the entering light repeats total reflection on the wall of the
light collector 703 while outgoing from the outgoing face in the
light-condensing film.
In terms of flexibility of a light-diffusing film in this
invention, it is necessary that a curvature radius as a measure of
bending resistance is 40 mm or less. When flexibility as a
curvature radius is 40 mm, a roll with a minimum diameter p=100 mm
used in a roll-to-roll process can be used.
It is necessary that a coefficient of thermal expansion of the
light-diffusing film in this invention is 50 ppm/.degree. C. or
less. A plastic material can have a reduced coefficient of thermal
expansion by containing an inorganic fillerss, and the
light-diffusing film may be made of any of those described later in
Example 1. An inorganic fillerss should be smaller than a
wavelength of visible light for maintaining transparency of the
film. When its particle size is 380 nm or less, there may be no
practical problems although transparency is deteriorated in the end
of the short-wavelength side in visible light. More preferably,
with a particle size of 1 to 100 nm, transparency is not
deteriorated over the whole visible range.
Examples of a light-diffusing film include a resin film with a
convexo-concave surface, a film in which two or more transparent
resins are combined in separate phases with convexo-concave
interfaces and a resin film containing light-scattering particles.
When using a film with an convexo-concave interface, it is not
necessary to make the film light-diffusing.
For a resin film containing light-scattering particles, the
light-scattering particles are preferably transparent and made of a
material having a refractive index different from that in the light
diffusing film; for example, resin beads, titanium dioxide, zinc
oxide, alumina, ITO and silicon oxide. A particle size of the
light-scattering particle may be 0.5 .mu.m or more, more preferably
1.0 .mu.m or more because within the range, a diffused light
becomes wavelength dependent and thus tinting can be avoided.
Furthermore, when a particle size of the light-scattering particle
is 1/2 or less of a thickness of the light diffusion functional
thin film, the particle does not affect light diffusing function;
more preferably 1/4 or less. For obtaining a coefficient of thermal
expansion of 50 ppm/.degree. C. or less, titanium dioxide, zinc
oxide, ITO, alumina or silica is preferable.
A content of the fillers is 0.1% by weight to 90% by weight both
inclusive, more preferably 0.5% by weight to 90% by weight both
inclusive. Adequate light-diffusing function can be in 0.1% by
weight or more while breakage due to brittleness can be avoided in
90% by weight or less. When using an inorganic material such as
zinc oxide, ITO and silica as fillers, a content of 5% by weight or
more may effectively reduce a coefficient of thermal expansion, and
10% by weight or more is more preferable.
In terms of light diffusion, a haze is preferably 30% or more. By
employing the above configuration, a haze of 30% or more can be
obtained (haze=(diffusion transmittance/total light transmittance)
(100%).
There will be an organic EL device as a backlight source in a
liquid-crystal panel as Embodiment 9 of this invention.
An organic EL device has a structure where an organic layer
comprising a light-emitting layer made of an organic light-emitting
material intervenes between an anode and a cathode facing each
other. Generally, in an organic EL device, one electrode is a
transparent electrode while the other electrode as a rear electrode
is an opaque metal electrode.
Organic EL devices can be classified into two types: bottom
emission type devices prepared by sequentially forming, on a
substrate, a transparent electrode with a high transmittance, an
organic layer comprising a light-emitting layer made of an organic
light-emitting material and a light-impermeable rear electrode,
where a light emitted from the light-emitting layer passes through
the substrate; and top emission type devices prepared by
sequentially forming, on a substrate, a rear electrode, an organic
layer comprising light-emitting layer made of an organic
light-emitting material and a transparent electrode where a light
emitted from the light-emitting layer passes through the
transparent electrode. The light-emitting layer may be made of a
low molecular-weight material or a polymer material.
There will be described a structure of a flat light emitting device
in this embodiment with reference to the drawings. It will be
described using an organic EL device as a specific example. It will
be, of course, understood that a device other than an organic EL
device, for example, an inorganic EL device, may be used as long as
a thin device structure can be formed.
A concept of a light emitting device consisting of an organic EL
will be described with reference to FIG. 7A. A light emitting
device consisting of an organic EL has a structure where on an
anode 122 made of transparent ITO (Indium Tin Oxide) are deposited
an organic EL layer 121 and a cathode layer 123 having a smaller
work function than that of the anode layer 122. Between a pair of
electrodes 122 and 123 in the organic EL device having such a
configuration, a desired power is applied from an unshown power
supply to initiate light emission (emitted light B) from the
organic EL layer 112 sandwiched between the electrodes 122 and
123.
The anode layer 122 may be made of a metal having a large work
function such as nickel, gold, platinum and palladium and their
alloys; a metal compound such as tin oxide (SnO.sub.2) and copper
iodide; or a conductive polymer such as polypyrrol. Commonly used
are transparent electrodes made of ITO.
A cathode layer 123 is preferably made of a material as a good
electron injector. Specifically, a metal material with a small work
function (low work-function metal material) whereby an electron
injection efficiency can be improved is used; generally, aluminum
and alloys such as magnesium-silver and aluminum-lithium. The
organic EL layer 112 may have, for example, a two-layer structure
where from the side of the anode layer 122 are sequentially
deposited a hole transport layer 124 and an organic light-emitting
layer 125. The hole transport layer may be made of
N,N'-diphenyl-N,N'-bis(3-methylphenyl)1,1'-biphenyl-4,4'-diamine
(triphenyldiamine; hereinafter, referred to as "TPD"), while the
organic light-emitting layer may be made of
tris(8-hydroxyquinalinato)aluminum
(Tris(8-hydroxyquinolinato)Aluminium, abbreviated as "Alq").
Besides the above structure, the organic EL layer 112 often
improves transportability of holes and electrons in three-layer
structure comprising a hole transport layer efficiently
transporting holes which is in contact with an anode electrode
(anode), a light-emitting layer containing a light-emitting
material and an electron transport layer efficiently transporting
electrons which is in contact with a cathode electrode (cathode).
In addition, there may be appropriately disposed a lithium fluoride
layer, a layer of an inorganic metal salt and/or layers comprising
thereof.
In the light-emitting layer 125, an emitted light outgoes from the
anode side as a transparent electrode.
FIG. 7B shows a schematic structure of an organic EL device as
another backlight source of this embodiment. On a substrate 114 is
deposited aluminum to be a cathode to 100 nm by a common sputtering
method. Subsequently, are sequentially deposited a light-emitting
layer 125 to be an organic EL layer 112 and a hole transport layer
124 to 100 nm each by an application method, and then an ITO film
to be an anode 122 to 100 nm by sputtering. Thus, an emitted light
(emitted light B) from the organic EL layer 112 outgoes from the
anode side.
FIG. 7C shows a modified backlight source where on a substrate are
sequentially deposited, as an organic EL device, an anode 122, a
hole transport layer 124, a light-emitting layer 125 and a cathode
3. A process for producing an organic EL layer and thickness of
each film are as described for FIG. 7B and thus are not
described.
For allowing the anode 122 to act as a reflection film, the
electrode in contact with the hole transport layer 124 is an ITO
film 127 having a laminate structure consisting of an electrode
made of transparent ITO and an aluminum film acting as a reflection
film 126. The aluminum film may be deposited to a thickness of 100
nm by sputtering as described for the cathode in FIG. 7B.
For outputting a light to the side of the cathode 123, it is
necessary that the aluminum film is sufficiently thin to prevent
deterioration in transparency, thus giving a laminated film with an
ITO film. After forming the aluminum film to 1 nm to 10 nm, a
transparent electrode film such as an ITO film may be deposited. In
this example, aluminum and an ITO film were deposited to 5 nm and
95 nm, respectively. When a thickness of the aluminum film is 1 nm
or more, electron injecting performance is not deteriorated, while
when it is 10 nm or less, transparency is not deteriorated.
For preparing a backlight source for a color liquid-crystal panel
(apparatus), a light emitted from the light-emitting layer should
be white (for example, daylight standard light source D65 (color
temperature: 6500 K)). There are no materials which alone can emit
a white light. A white light is, therefore, emitted by producing,
from a plurality of light-emitting material, a plurality of colored
lights, which are then combined. Combination of a plurality of
colored lights may involve production of three primary colors,
i.e., red, green and blue, or utilization of complementary color
system such as blue and yellow and blue-green and orange, but the
emitted light should be suitable for a spectral transmittance in
each color filter.
When using a color filter comprising thee filters of red, green and
blue, color display requires at least emitted lights at a
wavelength capable of passing through a red, a green and a blue
filters, respectively. If spectral transmittances of the red and
the green filters are discontinuous at a wavelength between them,
it is not necessary that a light at a wavelength which does not
pass through the red or the green filter is emitted. Furthermore,
when a light-emission maximum value is between green and blue, and
the light is at a wavelength which can pass through both blue and
green filters, it is not necessary that two colors of blue and
green are independently emitted.
Since a light-emitting part in an organic EL device is an organic
compound, the light-emitting part must be protected from an
external atmosphere (e.g., moisture, oxygen). Thus, it is desirable
to form, after forming the organic EL layer 112, a protective film
made of SiO.sub.2, SiN, Al.sub.2O.sub.3 or AlN as a continuous
operation.
When forming the organic EL layer 112 by vapor deposition, it is
preferable to form the protective film in the same vacuum chamber
by sputtering. Here, it is preferable to form, as a continuous
operation, the organic EL layer 112, the anode 122 made of
transparent ITO and the protective film in sequence. In terms of a
thickness of the protective film made of SiO.sub.2, SiN,
Al.sub.2O.sub.3 or AlN, 100 nm or more is adequate for protecting
the organic EL device. Although there are no particular restriction
to an upper limit of the thickness, 1 .mu.m or less is acceptable
in practical manufacturing.
The protective film preferably covers, as shown in FIGS. 7D and 7E,
the edge of the organic EL layer 112 as a light-emitting layer in a
thin film light emitting device and the upper surface of the
organic EL layer 112 which is not covered by a transparent
electrode 111.
There will be described a base film as Example 1 of this
invention.
EXAMPLE 1
Base Film
A base film to be a supporting substrate constituting a liquid
crystal display panel must be thin, heat resistant, transparent to
a light, particularly a visible light and optically isotropic,
i.e., having a small phase difference (optical lag).
Furthermore, in terms of flexibility, it desirably has a curvature
radius, r=40 mm or less as a measure of bending resistance. When r
is at least 40 mm, a roll having a minimum diameter of .phi.=100 mm
which is used in a roll-to-roll process can be used. In addition, a
liquid-crystal panel or a liquid crystal display comprising a
highly flexible supporting substrate is resistant to falling impact
because it can absorb the impact by bending, resulting in
improvement in shock resistance.
When a thin-shaped display device such as an electronic book is
manufactured, it can be bent like a conventional paperback such as
a pocket edition. Thus, it can be used without uncomfortable
feeling.
When being mounted as a display device in an apparatus for a mobile
application, it is essential that it is resistant to an impact and
falling. In a conventional glass substrate, shock resistance is
dependent on a part receiving a falling impact because of its
material properties, and thus an impact to an edge may readily
break the substrate. On the other hand, a plastic substrate
exhibits a higher shock resistance than a glass, but when it
receives an impact on an edge, the supporting substrate and a
transistor or interconnection mounted on the supporting substrate
are directly exposed to the impact as is in a glass substrate.
Reducing a weight of a liquid-crystal panel by improving
flexibility of the supporting substrate and thinning the supporting
substrate in the liquid crystal display panel may improve shock
resistance owing to weight reduction.
In terms of a thickness, there are no particular restrictions to an
upper limit when the substrate is used only in a roll-to-roll
process. However, in the light of size reduction and weight
reduction of the overall display device, the substrate is
preferably thinner than 400 .mu.m for a glass substrate, more
preferably thinner than 200 .mu.m for a plastic substrate. For
meeting the requirements of size reduction and weight reduction in
the overall display device, the thickness is preferably 10 to 150
.mu.m, more preferably 10 .mu.m to 100 .mu.m. When it is 10 .mu.m
or more, wrinkling or breakage during carrying can be
prevented.
In terms of heat resistance, the substrate is required to resistant
to optical and mechanical distortion at a temperature when a
functional film is formed. For the purpose of this, mechanical and
optical variation is preferably at least 5% or less to a
temperature history at 200.degree. C., more preferably 5% or less
to a temperature history at 250.degree. C.
The term "optical variation" refers to deterioration in optical
transparency and increase in a phase difference due to temperature
variation and the term "mechanical variation" refers to
deterioration in flexibility and variation in a dimension.
In terms of transparency, the substrate is required to be
transparent in the visible range (380 nm to 800 nm). It exhibits
higher transparency at least in the range of 450 nm to 700 nm, more
preferably 400 to 700 nm, further preferably 380 nm to 800 nm (the
visible range). When it exhibits higher transparency in the range
of 450 to 700 nm, it is practically acceptable. Transparency in the
range of 400 nm to 700 nm is more preferable and may be
substantially adequate even for a case where the most strict hue is
needed, but further preferably, it exhibits a high light
transmittance in the overall visible range of 380 nm to 800 nm. A
wider wavelength range exhibiting transparency may result in an
image display device capable of more precisely reproducing an
original color. It is substantially acceptable that to a desired
thickness of the base film, a light transmittance (wavelength; 550
nm) is 80% or more; more preferably 85% or more, further preferably
90% or more.
Examples of a plastic material for a base film in terms of heat
resistance include acrylic resins, epoxy resins, cyclic olefin
resins, polyimides and polyamides. Meanwhile, in terms of higher
transparency and optical isotropy, an acrylic resin or a cyclic
olefin resin may be preferably used.
For higher heat resistance, an acrylic resin is preferably an
acrylic or methacrylic compound which is at least difunctional,
more preferably at least trifunctional. Preferable examples include
bisphenol-A diacrylate, bisphenol-S diacrylate, dicyclopentadienyl
diacrylate, pentaerythritol triacrylate,
tris(2-hydroxyethyl)isocyanurate triacrylate, pentaerythritol
tetraacrylate, bisphenol-A dimethacrylate, bisphenol-S
dimethacrylate, dicyclopentadienyl dimethacrylate, pentaerythritol
trimethacrylate, tris(2-hydroxyethyl)isocyanurate trimethacrylate
and pentaerythritol tetramethacrylate, which may be used as a
mixture of two or more.
Examples of a cyclic olefin resin include addition (co)polymers of
a cyclic olefin compound, addition copolymers of ethylene and a
cyclic olefin compound and hydrogenated ring-opened (co)polymers of
a cyclic olefin compound. The hydrogenated compound can be prepared
by hydrogenating a ring-opened (co)polymer of a cyclic olefin in
the presence of a hydrogenation catalyst.
A cyclic olefin compound may be one or more selected from, for
example, bicyclo[2.2.1]hepta-2-ene,
5-methyl-bicyclo[2.2.1]hepta-2-ene,
5-ethyl-bicyclo[2.2.1]hepta-2-ene,
5-propyl-bicyclo[2.2.1]hepta-2-ene,
5-hexyl-bicyclo[2.2.1]hepta-2-ene,
5-decyl-bicyclo[2.2.1]hepta-2-ene,
5,6-dimethyl-bicyclo[2.2.1]hepta-2-ene,
5-methyl-5-ethyl-bicyclo[2.2.1]hepta-2-ene,
5-phenyl-bicyclo[2.2.1]hepta-2-ene,
5-cyclohexyl-bicyclo[2.2.1]hepta-2-enetricyclo[4.3.0.1.sup.2,5]deca-3-ene-
, tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodeca-3-ene,
3-methyl-tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodeca-8-ene,
3-ethyl-tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodeca-8-ene, methyl
2-methyl-bicyclo[2.2.1]hepta-5-ene-2-carboxylate,
2-methyl-bicyclo[2.2.1]hepta-5-ene acrylate,
2-methyl-bicyclo[2.2.1]hepta-5-ene methacrylate, dimethyl
bicyclo[2.2.1]hepta-5-ene-2,3-dicarboxylate, diethyl
bicyclo[2.2.1]hepta-5-ene-2,3-dicarboxylate,
3-methyl-3-methoxycarbonyl-tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodeca-8-
-ene, bicyclo[2.2.1]hepta-5-ene-N-cyclohexyl-2,3-maleimide,
bicyclo[2.2.1]hepta-5-ene-2-spiro-3'-N-phenylsuccinmide,
bicyclo[2.2.1]hepta-5-ene-2-spiro-3'-N-cyclohexylsuccinmide,
2-[(3-ethyl-3-oxetanyl)methoxy]bicyclo[2.2.1]hepta-5-ene,
2-[(3-ethyl-3-oxetanyl)methoxymethyl]bicyclo[2.2.1]hepta-5-ene,
(3-ethyl-3-oxetanyl)methyl-5-triethoxysilyl-bicyclo[2.2.1]hepta-2-ene
bicyclo[2.2.1]hepta-5-ene-2-carboxylate,
5-methyidimethoxysilyl-bicyclo[2.2.1]hepta-2-ene,
5-[1'-methyl-2',5'-dioxa-1'-silacyclopentyl]-bicyclo[2.2.1]hepta-2-ene,
5-[1'-methyl-3',3',4',4'-tetraphenyl-2',5'-dioxa-1'-silacyclopentyl]-bicy-
clo[2.2.1]hepta-2-ene,
5-[1',4',4'-trimethyl-2',6'-dioxa-1'-silacyclohexyl]-bicyclo[2.2.1]hepta--
2-ene.
Since a base film must show minimum dimensional change during a
process for manufacturing a display, a coefficient of thermal
expansion is preferably 50 ppm/.degree. C. or less. A coefficient
of thermal expansion of a plastic material can be reduced by adding
inorganic fillers. Inorganic fillers must be smaller than a
wavelength of the visible light for maintaining transparency of the
film, and a particle size of 380 nm or less is practically
acceptable although transparency may be deteriorated around at the
shortest wavelength of the visible light. More preferably a size of
1 to 100 nm can be used without deterioration in transparency in
the overall visible range. Although a size of 1 nm or less may be
acceptable, it is difficult to prepare fillers with a size of 1 nm
or less by current technique.
Examples of the inorganic fillers include titanium dioxide, zinc
oxide, alumina and silicon oxide. The inorganic fillers can be
incorporated, for example, by dispersing dry powdery silicon oxide
particles using a mixer having higher dispersing ability; by
blending a colloid (sol) dispersed in an organic solvent and other
components and removing the organic solvent in vacuo optionally
with stirring; or by blending a colloid (sol) dispersed in an
organic solvent and other components, removing the solvent as
necessary and then further removing the solvent by flow casting. An
example of an apparatus having higher dispersing ability is a bead
mill.
A plastic material into a film can be processed into a film by, for
example, melt extraction or solution casting. In processing an
acrylic or cyclic olefin resin, solution casting is preferably
used. An acrylic resin can be formed into a film by casting a neat
liquid monomer and curing it by heating or irradiation with an
active energy ray. For cyclic olefin resins, those having an acryl
or metharyl group in a side-chain substituent in a monomer unit can
be heated or irradiated with an active energy ray, those containing
an oxetanyl group can be treated with an acid generating agent, and
those containing a hydrolizable silyl group can be hydrolized by
liquid or gaseous hot water and subjected to condensation in the
presence of a tin compound as a catalyst, to give cured films.
An active energy ray used in the curing is preferably UV rays.
Examples of a lamp generating UV rays include a metal-halide lamp
and a high-pressure mercury-vapor lamp. In curing with an active
energy ray such as UV rays, preferably a photopolymerization
initiator which generates radical is added. Examples of a
photopolymerization initiator used here include benzophenone,
benzoin methyl ether, benzoin propyl ether, diethoxyacetophenone,
1-hydroxy-cyclohexyl phenyl ketone,
2,6-dimethylbenzoyl-diphenylphosphine oxide,
2,4,6-trimethylbenzoyl-diphenylphosphine oxide and benzophenone.
Two or more of these photopolymerization initiators may be
combined. A content of a photopolymerization initiator is
preferably 0.01 to 2 parts by weight to 100 parts by weight of an
organic component having a (meth)acryl group. A too low content may
lead to insufficient sensitivity to complete curing while a too
high content may lead to excessive sensitivity which may cause a
curing reaction during compounding, resulting in defective
application.
In thermal polymerization, a thermal-polymerization initiator may
be added as necessary. Examples of a thermal-polymerization
initiator used here include benzoyl peroxide, diisopropyl
peroxycarbonate and t-butyl peroxy(2-ethylhexanoate), which can be
used an amount of 0.01 to 1 parts by weight to 100 parts by weight
of an organic component having (meth)acryl group.
The base film of this example preferably has a higher transparency.
Specifically, it has a higher light transmittance and is optically
isotropic, i.e., a small phase difference. A light transmittance at
wavelength 550 nm is 85% or more, more preferably 90% or more. A
phase difference in a normal line direction is preferably 10 nm or
less, more preferably 5 nm or less.
A thickness of the base film in this invention is preferably 10 to
300 .mu.m. A thickness of less than 10 .mu.m may lead to wrinkles
or breakage during shipping while a thickness of more than 300
.mu.m may tends to make roll-to-roll processing difficult.
There will be described a specific process for preparing a base
film.
An acrylic resin type base film was prepared as follows. First,
were mixed 120 parts by weight of dicyclopentadienyl diacrylate and
400 parts by weight of isopropyl alcohol dispersion type colloidal
silicon oxide [silicon-oxide content: 30% by weight, average
particle size: 10 to 20 nm]. While stirring the mixture at
45.degree. C., volatile components were evaporated by 200 parts by
weight in vacuo. Then, to the mixture was added 0.6 parts by weight
of a photopolymerization initiator, 1-hydroxy-cyclohexyl phenyl
ketone (Ciba Specialty Chemicals Inc., "Irgacure 184"), and the
initiator was dissolved, to give a resin composition for a base
film.
Using an applicator (not shown), the resin composition for a base
film was applied by a die coater on a mold-release treated PET
(polyethylene terephthalate) film such that a film thickness was to
be 100 .mu.m after curing the resin composition for a base film.
Subsequently, in an oven controlled at 120.degree. C., volatile
components were evaporated and the residue was cured by a UV-ray
irradiation apparatus. After the curing, the PET film was released
from the mold to provide a base film.
A cyclic olefin resin type base film was prepared as follows. In
550 parts by weight of xylene were dissolved 100 parts by weight of
a bicyclo[2.2.1]hepta-2-ene addition copolymer containing 3 mol %
of 5-triethoxysilyl-bicyclo[2.2.1]hepta-2-ene having a
weight-average molecular weight of 230,000, 1.5 parts by weight of
tributyl phosphite and
pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate-
] and of tris(2,4-di-t-butylphenyl)phosphite as antioxidants (0.5
parts by weight each), to prepare a resin composition for a base
film.
Using an applicator (not shown), the composition was applied on a
PET (polyethylene terephthalate) film by a die coater, and
subjected to primary drying under gradual warming from 30.degree.
C. to 50.degree. C. to obtain a film containing a solvent in 20 to
50 parts by weight. The film was peeled off from the PET film,
exposed to a toluene-vapor atmosphere at 30.degree. C., then
subject to secondary drying at 50 to 200.degree. C., and then
exposed to a hot moisture atmosphere at 170.degree. C. to provide a
cured base film with a thickness of 100 .mu.m.
In the acrylic resin type base film thus obtained, a light
transmittance was 90% (550 nm, thickness: 100 .mu.m), a phase
difference was 3 nm, and a Young's modulus was 5.3 GPa. In the
cyclic olefin resin type base film, a light transmittance was 91%
(550 nm, thickness: 100 .mu.m), a phase difference was 5 nm, and a
Young's modulus was 2.9 GPa.
When 25% by weight of silicon oxide with an average particle size
of 300 nm (maximum particle size: 400 nm) was added, no changes in
a light transmittance, a phase difference or a Young's modulus were
observed. When adding an inorganic fillers, a coefficient of
thermal expansion was improved from 85 ppm/.degree. C. to 35
ppm/.degree. C. in the acrylic resin type and from 80 ppm/.degree.
C. to 38 ppm/.degree. C. in the cyclic olefin resin type.
Both acrylic and cyclic-olefin resin types exhibited flexibility
such that they could be wound into a roll with a radius of 30
mm.
An initial value was retained after storing at an high-temperature
of 270.degree. C. for 24 hours. Mechanical or optical deterioration
was observed after storage at an elevated storage.
There will be described a specific process for forming a gas
barrier layer on a base film.
Since a base film is a thin film made of an organic resin, common
air components such as oxygen and moisture enters a liquid crystal
layer and an organic EL layer. A gas barrier layer must be
transparent because the substrate must transmit a light. Thus,
examples of a material of the gas barrier layer include organic
materials such as polyvinyl alcohols; organic-inorganic composite
materials such as those of an organic material with an inorganic
material including a clay mineral (an amorphous clay mineral such
as Al.sub.2O.sub.3-2SiO.sub.2.5H.sub.2O and
Al.sub.2O.sub.3SiO.sub.2.2-3H.sub.2O, or a crystalline clay mineral
such as (Si,Al)O.sub.4 tetrahedral sheet and (Al,Mg)(O,OH).sub.6
octahedral sheet); and a thin film of an inorganic material such as
silicon oxide and aluminum oxide. A film thickness may be more
reduced by using an inorganic material because it exhibits good gas
barrier properties under a high humidity atmosphere and is
effective with a smaller thickness. Furthermore, two or more of
these layers may be deposited.
A thickness of a gas barrier layer is preferably 1 to 10 .mu.m when
it is made of an organic material or an organic-inorganic composite
material and preferably 10 nm to 1 .mu.m when it is made of an
inorganic material. When it is made of an organic material or an
organic-inorganic composite material, a thickness of 1 .mu.m or
more can adequately prevent common air components such as oxygen
and moisture from entering a liquid crystal layer or an organic EL
layer. A thickness of 10 .mu.m or less does not influence
properties of the base film such as an expansion coefficient. When
it is made of an inorganic material, a thickness of 10 nm or more
can adequately prevent common air components such as oxygen and
moisture from entering a liquid crystal layer or an organic EL
layer, while a thickness of 1 .mu.m or less can prevent breakage
during bending.
A gas barrier layer can be formed on a film by an application
method for an organic material or an organic-inorganic composite
material and by any of various film deposition methods for an
inorganic material. In an application method, a liquid such as a
liquid organic material or a solution thereof is applied on a film
and is dried or cured to form a film. Examples of film deposition
include physical growth methods such as vacuum vapor deposition,
ion plating and sputtering; and chemical vapor growth methods such
as plasma CVD in vacuo, catalytic CVD and CVD under an atmospheric
pressure. Among these, sputtering is particularly preferable
because it can provide a dense film at a low temperature.
There will be described a specific process for forming a gas
barrier layer.
A roll 2 of a base film 3 with a thickness of 100 .mu.m, a width of
30 cm and a length of 100 m was set in the side of a wind-off roll
in a magnetron sputter roll coater shown in FIG. 8. Argon and
oxygen were introduced as a discharge gas and a reactant gas,
respectively at a deposition pressure of 0.3 Pa and a
temperature-controlling drum temperature 30.degree. C., and then,
using boron-doped silicon as a target, a pulse DC power source was
operated to initiate reactive sputtering film deposition. An input
electric power and a carrying speed were adjusted to deposit a gas
barrier layer of silicon oxide (SiO.sub.x; x is 1.6 to 1.9) with a
thickness of 100 nm. After the deposition, the vacuum chamber was
returned to an atmospheric pressure and then opened. Then, a film
with a gas barrier layer was removed from the side of the wind-up
roll 11.
Although the gas barrier layer was formed in one side of the base
film in this example, it can be formed in both sides. In such a
case, the layer may be formed in one side before a gas barrier is
formed in the other side in a similar manner, or alternatively,
while placing the target 5 shown in FIG. 8 in both front and rear
sides, gas barrier films can be deposited on both sides in the base
film in one step.
Although a magnetron sputter was used in this example, another
sputtering method or vapor deposition may be employed. Chemical
deposition may be used, but a configuration of a manufacturing
apparatus is simpler in physical deposition.
FIGS. 9 and 10 show the manufacturing steps of transferring a
thin-film transistor from a glass substrate to a base film as
Example 2.
EXAMPLE 2
Thin-Film Transistor
There will be described the step of forming a thin-film transistor
(TFT: Thin Film Transistor) on a glass substrate with reference to
FIG. 9. As shown in FIG. 9A, on a glass substrate 201 is deposited
a barrier film 202 as an oxide or nitride film to be an antietching
layer to hydrofluoric acid, on which is then deposited an amorphous
or polysilicon film. In this example, an amorphous silicon film
216a was deposited to 100 nm. These thin films can be deposited by,
for example, plasma CVD or sputtering. Then, as shown in FIG. 9B,
an excimer laser beam is irradiated to modify the amorphous silicon
film into a polysilicon film 216b. Here, modification into a
polysilicon film can be conducted by, in place of laser beam
irradiation, solid-phase growth by thermal annealing.
As shown in FIG. 9C, a polysilicon film 216b is patterned into a
desired shape, on which a gate insulating film 217 as an oxide film
is then deposited to 100 nm by, for example, plasma CVD or
sputtering. Then, as shown in FIG. 9D, a gate electrode 218 is
formed, an area in which an n-channel transistor is to be formed is
covered by a photoresist and then boron is implanted (D) by ion
doping to form a p-type area Fa. Subsequently, as shown in FIG. 9E,
an area in which a p-channel transistor is to be formed is covered
by a photoresist 219 and phosphorus is implanted (E) by ion doping
to form an n-type area Fb. Then, as shown in FIG. 9F, a source and
a drain electrodes made of aluminum are formed. Then, an
inter-layer insulating film 220 as an oxide film is formed to 200
nm and a metal electrode 221 made of aluminum is formed to provide
a transistor. A pixel-driving transistor unit for driving pixels in
a liquid-crystal panel may be constituted by an n-MOS or p-MOS
transistor alone. Such a transistor array can be appropriately
arranged to form a desired circuit on a glass substrate. Then, in
an area to be an image display unit, a transparent conductive film
such as ITO is further deposited to form a desired pixel electrode.
Finally, an oxide film with a thickness of 200 nm is formed as an
electrode protective film for protecting the electrode. Thus, there
is provided a TFT glass substrate for a liquid crystal display
panel.
Next, there will be described a process for forming a device film
on a base film by transferring the above transistor for a liquid
crystal display panel on the base film with reference to FIG.
10.
As shown in FIG. 10A, a protective film 230 is glued, with an
adhesive, on a transistor-forming surface in a glass substrate 201
having a transistor array 229. Then, as shown in FIG. 10B, the
substrate with the protective film is immersed in a glass etching
solution of hydrofluoric acid 231 to etch a glass substrate 228
from its rear surface. Etching is terminated at a barrier layer 234
after etching the glass substrate 228 off.
In addition to hydrofluoric acid, buffered hydrofluoric acid may be
suitably used as a glass etching solution. After completely etching
the glass substrate off, a base film 235 is laminated with the
etching surface as shown in FIG. 10C. Finally, as shown in FIG.
10D, the protective film 230 and the adhesive are removed to
complete transfer, giving a device layer formed on the base film.
Here, the barrier film 202 in FIG. 9A may also act as an etching
stopper when its etching rate is lower to the glass etching
solution, so that the glass substrate etching step in FIG. 10B can
be satisfactorily controlled. In addition, the protective film 230
must be made of a material resistant to a strong acid such as
hydrofluoric acid. During etching, temperature variation in the
etching solution must be prevented for uniform etching.
As described above, a TFT film substrate for a liquid crystal
display panel can be prepared.
In this example, a supporting substrate is a glass substrate, an
etching solution such as hydrofluoric acid is used for removing the
supporting substrate, a barrier layer is a nitride film and a
protective film is glued with an adhesive. Alternatively, for
example, a substrate may be a quartz or silicon substrate, the
supporting substrate may be removed by polishing and/or a hot-melt
sheet which is glued by heating can be used.
There will be more specifically described a functional thin film
such as a retardation film with reference to Examples. Before
described Examples, a film on which a functional thin film is
formed will be detailed.
The base film detailed in Example 1 is a film to be a substrate
constituting a panel by forming a liquid-crystal panel. A
supporting film for a functional film prepared in an intermediate
step may be, but not limited to, the base film. Examples of a
material which may be used for the supporting film include, besides
those which can be used for the base film, polyesters,
polyethylenes, polypropylenes, polyethylene terephthalates,
polyvinyl alcohols, epoxy resins, polyimides, polyamides,
polystyrenes, polycarbonates, polyolefins (e.g., polypropylene),
polyhalogenated vinyls (e.g., polyvinyl chloride and polyvinylidene
chloride), ethylene vinyl copolymers, vinyl acetates, or cellulose
derivative resins (e.g., cellulose acetate, nitrocellulose and
cellophane). A cover film may be made of a material as described
for the supporting film. Of course, a material is appropriately
changed, depending on the conditions during forming the functional
thin film such as a light transmittance and a temperature condition
during production.
In both cover film and supporting film, a coefficient of thermal
expansion is preferably 50 ppm/.degree. C. or less and a difference
in a coefficient of thermal expansion in the base film is
preferably .+-.30% or less, more preferably .+-.15% or less. Since
a functional thin film formed on a supporting film is transferred
to a functional thin film on a base film, it is particularly
necessary to match a coefficient of thermal expansion in the
supporting film with that in the base film.
In Examples below, a film meeting the above conditions is, of
course, used, although no supporting film properties are
particularly described.
In particular, it is necessary that when an optically functional
thin film is not a thermally curable resin but a photocurable
resin, a particle size of an inorganic fillers added to the resin
is 1 nm to 200 nm, more preferably 1 nm to 150 nm. The lower limit
is not restricted to 1 nm, and if the film can be manufactured, a
thickness of 1 nm or less may be acceptable.
When adding an inorganic fillers (silicon oxide) with an average
particle size of 150 nm (maximum particle size: 200 nm) to the
acrylic resin type base film in Example 1 in an amount of 30% by
weight, a transmittance of UV rays with a wavelength of 200 nm to
300 nm was 80%, which corresponded to adequate transparency for
permitting curing by irradiating a photocurable resin formed on a
film with UV rays from the bottom surface of the film.
There will be described a retardation film as Example 3 of this
invention.
EXAMPLE 3
Retardation Film
Application Type Retardation Film
Retardation films can be classified into application type
retardation films and lamination type retardation films. First, an
application type retardation film will be described.
Using a flexo press, on a roll of a base film roll made of a
polyether sulfone surface-treated with silicon oxide was applied a
polyimide orienting agent "AL-1254" (JSR Corporation) as an
oriented film, which was then dried at 180.degree. C. for 1 hour
and rubbed with a rayon cloth.
In addition, a coating film of an alkyl-chain modified poval (for
example, Kuraray Co., Ltd., MP203 or R1130) may be endowed with
such orienting ability by rubbing without firing. Furthermore, most
organic polymer films which form a hydrophobic surface such as
polyvinyl butyral and polymethyl methacrylate may be endowed with
liquid crystal orienting ability by rubbing its surface.
A silicon dioxide oriented film may be deposited as described in
Embodiment 2. It should be noted that it is formed by oblique
deposition.
A polymerizable liquid crystal composition (A) was prepared from 50
parts by weight of a compound represented by formula (10):
##STR00013## and 50 parts by weight of a compound represented by
formula (11):
##STR00014## The composition thus prepared showed a nematic phase
at room temperature, and a transition temperature from a nematic
phase to an isotropic phase was 47.degree. C. An n.sub.e
(extraordinary-ray refractive index) and n.sub.o (ordinary
refractive index) at 25.degree. C. were 1.65 and 1.52,
respectively. In methyl ethyl ketone was dissolved a polymerizable
liquid crystal composition (C) consisting of 100 parts by weight of
the polymerizable liquid crystal composition (A) and 1 part by
weight of a photopolymerization initiator "IRG-651" (Ciba-Geigy).
The solution was applied on the base film roll previously prepared,
using a gravure coater, and then irradiated with UV rays at 365 nm
at room temperature to 160 mJ/cm.sup.2 for initiating curing of the
polymerizable liquid crystal composition, to form a retardation
film with a thickness of 1.6 .mu.m. It was observed that the
retardation film had a phase difference of 138 nm to a light with a
wavelength of 550 nm and acts as a 1/4 wavelength plate. Lamination
Type Retardation Film
There will be described an example of a lamination type.
In N-methyl-2-pyrrolidone (hereinafter, referred to as "NMP") were
dissolved 85 mol % of 2-chloroparaphenylenediamine as an aromatic
diamine and 15 mol % of 4,4'-diaminodiphenyl ether. To the solution
was added 99 mol % of 2-chloroterephthalic dichloride, and the
mixture was stirred for 2 hours to complete polymerization. The
solution was neutralized with lithium hydroxide to give a solution
of an aromatic polyamide with a polymer concentration of 10% by
weight.
The polymer solution was cast on an endless belt, dried by hot air
at 150.degree. C. until it became self-supported and then peeled
off from the belt. The film peeled from the belt was extended to a
1.10-fold length in a longitudinal direction of the film in a water
bath at 40.degree. C. while the residual solvent and inorganic
salts were removed. Then, it was fed into a tenter, in which it was
dried and heated by hot air at 280.degree. C. It was then extended
to a 1.5-fold length in a width direction in the tenter to give an
aromatic polyamide film with a thickness of 4.0 .mu.m.
Phase differences of this film were R(550)=140 nm, R(450)=164 nm
and R(650)=126 nm. Thus, the film can act as a film for a
1/4.lamda. plate even when it has a 1/10 or less thickness in
comparison with a conventional film.
A lag axis in this film was matched with the width direction. A
dimensional change rate of the direction was 0.02%, a dimensional
change rate in an orthogonal direction was 0.0%, and Young's moduli
in a longitudinal direction (MD) and a width direction (TD) were 10
GPa and 16 GPa, respectively. They indicate that the film is
considerably heat resistant and tension resistant.
The film had a minimum light transmittance of 80% within 450 to 700
nm and a light transmittance of 24% at 400 nm.
Then, the polymer solution was cast on a belt and a self-supported
film was peeled off from the belt. The film was contacted with a
roll heated to 100.degree. C., and extended to a 1.8-fold length in
a longitudinal direction by inter-roll extension. Next, the film
extended in the MD direction was fed into a water bath at
40.degree. C., and after removing the residual solvent and
inorganic salts, introduced into a tenter. In the tenter, it was
dried and heated by hot air at 300.degree. C. It was then extended
to a 2.2-fold length in a width direction in the tenter to give an
aromatic polyamide film with a thickness of 3.0 .mu.m. Phase
differences of this film were R(550)=278 nm, R(450)=326 nm and
R(650)=252 nm. Thus, the film can act as a film for a 1/2.lamda.
plate even when it has a 1/10 or less thickness in comparison with
a conventional film.
A lag axis in this film was matched with the width direction. A
dimensional change rate of the direction was 0.04%, a dimensional
change rate in an orthogonal direction was 0.0%, and Young's moduli
in a longitudinal direction (MD) and a width direction (TD) were 19
GPa and 9 GPa, respectively. They indicate that the film is
considerably heat resistant and tension resistant.
The film had a minimum light transmittance of 79% within 450 to 700
nm and a light transmittance of 22% at 400 nm.
The retardation film described above is preferably laminated on a
supporting film.
An aromatic polyimide or polyamide acid solution in this example is
prepared as follows. A polyamide acid can be prepared by reacting a
tetracarboxylic acid dihydrate and an aromatic diamine in an
aprotic organic polar solvent such as N-methylpyrrolidone,
dimethylacetamide and dimethylformamide. An aromatic polyimide can
be prepared by heating the solution containing the above polyamide
acid or alternatively by adding an imide-forming agent such as
pyridine to obtain polyimide powder, which is then redissolved in a
solvent. A polymer concentration in a deposition stock solution is
preferably about 5 to 40 wt %.
The deposition stock solution can be used to form a retardation
film. The retardation film thus obtained exhibited properties
comparable to a retardation film made of an aromatic polyamide.
Herein, physical properties were determined and effects were
evaluated as follows.
(1) Phase Difference
Determined by the following measuring apparatus.
Apparatus: Cell gap inspection system RETS-1100(Otsuka Electronics
Co. Ltd.)
Measuring diameter: .phi. 5 mm
Measuring wavelength: 400 to 800 nm
Phase differences at wavelengths 450 nm, 550 nm and 650 nm
determined as described above were R(450), R(550) and R(650),
respectively.
(2) Dimensional Change Rate at 150.degree. C.
A. Determination of a Lag Axis
A sample was placed on a universal stage and observed under crossed
nicols by a polarization microscope. A direction with the maximum
birefringence was defined as a lag axis. Alternatively, it may be a
direction with the maximum molecular orientation as determined by
an orientation meter (for example, Kanzaki Paper Co. Ltd.,
MOA-2001A).
B. Determination of a Dimensional Change Rate
Samples with a size of 150 mm (width: 10 mm) are taken in a lag
axis direction and a direction orthogonal thereto. To the samples
are marked reference lines at intervals of 100 mm in the
longitudinal direction. The samples are placed in a hot-air oven
without load and heated at 150.degree. C. for 10 min. The samples
are removed, cooled to an ambient temperature and spread on a
polyvinyl chloride sheet such that no wrinkles are formed. A
distance between reference lines (L: mm) are measured and a
dimensional change rate is calculated in accordance with the
following equation. Dimensional change rate (%)=(|L-100|/100)(100
(3) Transparency of a Film (Light Transmittance)
Measured using the following apparatus. A transmittance (%) for a
light at each wavelength is determined. Transmittance (%)=T1/T0
wherein T1 is an intensity of a transmitted light through a sample,
and T0 is an intensity of a light traveling by a certain distance
in the air without passing through the sample.
Apparatus: UV meter U-3410 (Hitachi Instruments Co. Ltd.)
Wavelength range: 300 nm to 800 nm
Measurement speed: 120 nm/min
Measurement mode: transmission
(4) Young's Modulus
Determined at a temperature of 23.degree. C. and a relative
humidity of 65% using Robot Tensiron RTA (Orientec Co. Ltd.). A
test piece has a width of 10 mm and a length of 50 mm, and an
extension speed is 300 mm/min. A point when a load passes 1N after
the start of the test was defined as the origin of extension.
There will be described a polarizing film as Example 4 of this
invention.
EXAMPLE 4
Polarizing Film
There will be described a polarizing film as Example 4 of this
invention.
A polarizing film used in this example can be prepared by
adsorption of iodine and/or a dichroic coloring agent such as a
dichroic dye by a polyvinyl alcohol film made of a polyvinyl
alcohol, a partially formated polyvinyl alcohol or a partially
saponified ethylene-vinyl acetate copolymer, two-axis extension and
then boric acid treatment. The polarizing film has a thickness of,
but not limited to, about 5 to 50 .mu.m.
A so-called H film (polyvinyl butyral film) can be used, which is
prepared by extending a polyvinyl alcohol thin film with heating
and immersing the film in a solution containing a large amount of
iodine (generally, called an "H ink"). The H film could give a film
with a thickness of 18 .mu.m.
An additional example is a polarizing film prepared by shaping a
resin pellet containing iodine and/or dichroic dye into a film by,
for example, melt extrusion or solution casting, and uniaxially
drawing the film to form a polarizing film in which iodine and/or a
dichroic dye is strongly oriented in one axis direction. The
polarizing film has a thickness of, but not limited to, about 1 to
10 .mu.m.
Such a method can also provide a polarizing film with a film
thickness of 10 .mu.m to 20 .mu.m. Examples of a resin used herein
include polyvinyl alcohol resins such as polyvinyl alcohols,
partially formated polyvinyl alcohols and partially saponified
ethylene-vinyl acetate copolymers; polyester resins such as
polyolefin resins, acrylic resins, PET (polyethylene terephthalate)
and PEN (polyethylene naphthalate); polyamide resins; polyamide
imide resins; polyimide resin; polycarbonate resins; and
polysulfone resins.
The polarizing film is laminated on a supporting film by heat,
pressure, a glue or an adhesive. The polarizing film is peeled off
from the supporting film and then laminated on, for example, a
protective film in an organic EL light emitting device on a
functional film.
When the polarizing film is formed on a mold-releasing film to be a
matrix base, only a polarizing function layer must be laminated on,
for example, a protective film in an organic EL light emitting
device on a functional film. It is, therefore, necessary that the
polarizing film and the supporting film are peelably laminated.
Furthermore, in the light of the fact that another layer is further
deposited on the surface after peeling off the supporting film, the
supporting film must be treated such that a mold release on the
supporting film does not transfer to the polarizing film during the
peeling.
The polarizing film must be protected from moisture or UV rays.
Such protection can be achieved by laminating an optically
transparent protective layer on one or both surfaces. A resin
constituting the protective layer must be not only optically
transparent and mechanically strong, but also heat resistant and
moisture-proof. Examples of such a resin include cellulose,
polycarbonates, polyesters, acrylic compounds, polyether sulfones,
polyamides, polyimides and polyolefins. Among these, preferred are
celluloses such as triacetylcellulose; polyesters such as
polycarbonates and polyethylene terephthalate; and acrylic
compounds.
A light from a light-emitting diode (LED) or organic EL device
little contains UV ray components. When a light-emitting diode
(LED) or organic EL device is used as a backlight in a
liquid-crystal panel, UV-ray resistance should not be considered.
Furthermore, an organic EL device is made of an optically
transparent inorganic material such as SiO2, SiN, Al2O3 and AlN for
protecting an organic material to be a light-emitting layer in the
organic EL device from moisture and/or oxygen.
A polarizing film for a backlight is often placed just over a
protective film in an organic EL. In such a case, a protective film
on one side of the polarizing film can be omitted. It is,
therefore, not necessary to form a protective film for a polarizing
film as in the prior art, so that a thinner polarizing film can be
obtained.
A protective film may be formed on a polarizing film by directly
laminating the polarizing film with the protective film for a
polarizing film, or alternatively by first laminating the
protective film for a polarizing film and a polarizing film on each
matrix base and then peeling off the protective film for a
polarizing film or the polarizing film from the matrix base while
laminating it on the polarizing film or the protective film for a
polarizing film. When using it as a polarizing film in a
liquid-crystal panel, for example, when using an organic EL device
as a backlight, it is preferable to laminating the polarizing film
on a protective film for a polarizing film because the polarizing
film is formed on the protective film in the organic EL device.
In this example, a total film thickness was 6 .mu.m, i.e., a
polarizing film (3 .mu.m)+a protective film (3 .mu.m).
When forming a protective film on one or both surface of a
polarizing film, it is formed by lamination of an optically
transparent protective layer. A resin constituting the protective
layer must be not only optically transparent and mechanically
strong, but also heat resistant and moisture-proof. Examples of
such a resin include cellulose, polycarbonates, polyesters, acrylic
compounds, polyether sulfones, polyamides, polyimides and
polyolefins. Among these, preferred are celluloses such as
triacetylcellulose; polyesters such as polycarbonates and
polyethylene terephthalate; and acrylic compounds.
The protective layer may contain a UV-ray absorber such as
salicylate compounds, benzophenol compounds, benzotriazole
compounds, cyanoacrylate compounds and nickel complex salt
compounds. Each surface of the protective layer may be processed by
various methods to have, for example, a hardcoat layer, an
antireflection layer and an antiglare layer.
A thickness of a protective layer is generally 80 .mu.m or less,
preferably 40 .mu.m or less in the light of, for example, weight
reduction, protecting function, handling properties and crack
resistance during cutting in the thin film. When forming protective
layers on both surfaces of a polarizer, these protective layers may
be made of different resins.
An adhesive is used for laminating a protective film with a
polarizer. There are no particular restrictions to an adhesive used
herein as long as it can adequately gluing the protective film with
the polarizer. An adhesive is applied on one or both surfaces of
the polarizer by any of various methods such as a wire bar, a
doctor blade and dipping and the polarizer is laminated with a
protective layer. Furthermore, for ensuring an adhesive power in
lamination, the adhesive layer is dried or cured by hot air, UV
rays or infrared ray. Here, it is preferable to dry or cure the
adhesive layer under the conditions which do not deteriorate
polarizing performance of the polarizer.
Furthermore, the polarizing film comprises a glue layer because the
film is laminated with a variety of optically functional members
such as a liquid crystal cell or a retardation film in a liquid
crystal display panel.
Such a glue may be selected from those containing a base polymer
such as acrylic polymers, silicone polymers, polyesters,
polyurethanes and polyethers. In particular, it is preferable to
select from those which exhibits good optical transparency,
appropriate wettability, appropriate cohesion force, good
adhesiveness to a base material, weather resistance and heat
resistance and can be used without peeling problems such as lift
and detachment; for example, an acrylic glue.
A useful base polymer for an acrylic glue is an acrylic copolymer
with a weight-average molecular weight of 100,000 or more prepared
by blending an alkyl(meth)acrylate having an alkyl group with 20 or
less carbon atoms such as methyl, ethyl and butyl with an acrylic
monomer consisting of, for example, (meth)acrylic acid or
hydroxyethyl(meth)acrylate such that a glass transition temperature
becomes preferably 25.degree. C. or less, more preferably 0.degree.
C. or less.
A gluing layer can be formed on a polarizing film, for example, by
dissolving or dispersing a glue composition in an organic solvent
such as toluene and ethyl acetate to prepare a 10 to 40% by weight
solution, which is then directly applied on a polarizing film to
form a glue layer, or alternatively by preliminarily forming a glue
layer on a protective film and transferring the glue layer on a
polarizing film to form a glue layer. A thickness of the gluing
layer depends on its adhesive power, and generally within a range
of 1 .mu.m to 50 .mu.m.
A gluing layer may, if necessary, contain fillerss such as glass
fiber, glass beads, resin beads, metal powder and other inorganic
powders; pigments; antioxidants; and UV absorbers such as
salicylate compounds, benzophenol compounds, benzotriazole
compounds, cyanoacrylate compounds and nickel complex salts. A
thickness of the above polarizing film is 150 .mu.m or less,
preferably 100 .mu.m or less in a configuration with protective
layers in both surfaces (protective layer/polarizer/protective
layer/glue layer) and 100 .mu.m or less, preferably 50 .mu.m or
less in a configuration with a protective layer in one surface
(protective layer/polarizer/glue layer).
When using a polarizing film according to this invention in a
reflection type or semi-transmissive reflection type liquid crystal
display panel, it may be laminated with a retardation film to be
used as a circularly-polarized light film.
Examples of a retardation film include films made of, for example,
polycarbonate, polyvinyl alcohol, polystyrene, polymethyl
methacrylate, polyolefin, polyarylate or polyamide whose in-plane
refractive index is controlled by uniaxial or biaxial drawing;
films whose refractive index in a thickness direction is controlled
by shrinking the raw-material resin film under adhesion to a
thermally shrinkable film; and oriented films of a discotic liquid
crystal or nematic liquid crystal. Here, two or more of the
retardation films may be combined for improving contrast.
It is preferable to use a glue for integrating a polarizing film
and a retardation film in the light of convenience in working and
prevention of optical distortion. Here, a glue layer may be formed
on one or both surfaces of the polarizing film or the retardation
film before integrating them. A glue layer formed may consist of
superimposed layers made of different compositions or types.
Furthermore, when forming glue layers on both surfaces, their
compositions or types may be different between the front and the
rear surfaces of the polarizing film or the optical layer.
When using a 1/4 wavelength plate as a retardation film, it is
necessary to laminate the film such that an angle between an
absorption axis of the polarizing film and a lag axis of the
retardation film is within the range of 45.degree..+-.1.degree. or
135.degree..+-.1.degree.. If lamination precision deviates from the
range, adequate function as a circularly-polarized light film
cannot be achieved.
In the above circularly-polarized light film, it is preferable to
employ a configuration that a retardation film is laminated on one
side of a polarizer via a glue layer (protective
layer/polarizer/glue layer/retardation film/glue layer), using a
polarizing film having a protective layer in one side. A thickness
of the circularly-polarized light film having such a configuration
is desirably 150 .mu.m or less, preferably 100 .mu.m or less.
A polarizing film according to this invention and a
circularly-polarized light film therewith are suitably used in a
liquid crystal display panel for a mobile device such as a notebook
personal computer and a cellular phone, and laminated one or both
sides of the liquid crystal cell via a glue. The polarizing films
or the circularly-polarized light films formed in both sides of the
liquid crystal cell may be the same or different. The film may be
laminated on the liquid crystal cell by, but not limited to,
preliminarily cutting the polarizing film or the
circularly-polarized light film substantially into the size of the
liquid crystal cell and applying a pressure to the film using a
roll or press such that no bubbles enter between the liquid crystal
cell and the polarizing film or the circularly-polarized light film
without the liquid crystal cell being broken.
There will be detailed a color filter as Example 5.
Film Type Color Filter
There will be described a process for manufacturing a film type
color filter as Example 5 with reference to FIG. 11. On a PET
(polyethylene terephthalate) film 390 wound-up as a roll with a
film thickness of 30 to 100 .mu.m to be a first supporting
substrate is applied, by an appropriate application method such as
gravure coating, a photosensitive resin layer 391 with a coating
film thickness of 10 .mu.m of red (R) 395, green (G) 396 or blue
(B) 397 to be a color filter or black (BK) 394 to be a black
matrix. A coating film thickness of the photosensitive resin layer
391 is preferably 5 .mu.m to 20 .mu.m, more preferably 8 .mu.m to
15 .mu.m. When the thickness is 5 .mu.m or more, the film can
satisfactorily act as a color filter or black matrix. When the
thickness is 20 .mu.m or less, a light transmittance is not
reduced.
In terms of a photosensitive resin layer 391, a coating film
thickness is 10 .mu.m and a film thickness of a color filter layer
after drying is 1 .mu.m.
The photosensitive resin layer is composed of a solvent component
and a solid component. The solid component consists of a
transparent resin component, a dispersing agent and a pigment. The
transparent resin component consists of a polymerization initiator,
a monomer and a thermal or optical cross-linking agent. The solvent
component may be selected from ketones, esters and ethers with a
boiling point of 100.degree. C. to 200.degree. C. and a vapor
pressure of 10 mmHg or less. The monomer is preferably a
polyfunctional acrylate monomer. If it is 10 mmHg or less, drying
spot can be avoided. As a thermal or optical cross-linking agent, a
(meth)acrylic acid-acrylate copolymer is desirable because it can
improve a visible-light transmittance. A photopolymerization
initiator is preferably selected from imidazole, acetophenone,
triazine and thioxanthone initiators because they can minimize a
dark reaction. In terms of a pigment, a particle size of 0.1 .mu.m
or less is acceptable because a light transmittance is not
deteriorated.
In addition to a polyethylene terephthalate resin, the supporting
substrate may be made of a resin selected from polyethylene resins,
polypropylene resins, polyester resins, ethylene vinyl copolymer
resins, polyvinyl chloride resins, cellulose resins, polyamide
resins, polyimide resins, polycarbonate resins, polystyrene resins
and vinyl acetate resins which are light-transmittable.
A film made of a polymer material for the first supporting
substrate is advantageous in that in subsequent steps, a
photosensitive resin 391 can be peeled off from the supporting
substrate, washed and then reused.
There will be detailed the step of forming a black matrix with
reference to the drawings. On a PET film 390 is applied a
photosensitive colored resin 391 consisting of a material selected
from carbon black, acetylene black and lampblack with a particle
size of 5 nm to 200 nm and a cross-linking agent having a carboxyl
group such as (meth)acrylamide and N,N-dimethyl(meth)acrylamide by
a die head method or a gravure roll method, and the resin is dried
at 180.degree. C. using hot air, infrared ray or far-infrared ray.
After cooling to an ambient temperature under cool air, a cover
film 392 made of a polyester resin is laminated on the
photosensitive colored resin 391, and then the film is wound into a
wind-up roll (FIG. 11A).
Only in a black matrix, a chromium layer may be formed to a
thickness of 0.1 .mu.m to 0.2 .mu.m. Although chromium can be
deposited by physical vapor deposition, an organic resin film is
more desirable herein.
There will be described preparation of a base film on which
photosensitive resins to be R (red), G (green) and B (blue) in a
color filter are similarly applied.
Next, from the wind-off roll is fed the base film 390 as a first
base in which the cover film 392 is laminated with the
photosensitive resin 391 for a black matrix while peeling off the
cover film. Then, on the surface with a cover film 392 is laminated
a second base 393 for a color filter made of a highly heat
resistant resin. Subsequently, the film is exposed from the side of
the base film 390 via a mask, the base film 390 is peeled, and the
photosensitive resin 391 is developed to form a black matrix on the
color filter base 393. Then, the cover film 392 is laminated on the
surface in which the black matrix is formed (see FIG. 11B).
The cover film is a protective film for the photosensitive resin
392, the black matrix and the color filter, and is desirably
weakly-adhesive so that it can be easily glued or peeled.
As used herein, weak adhesion means that the material can be
released together with a base supporting a gluing layer without
chemical or physical influence on the other material during
peeling. Such property can be achieved by dissolving a film made of
a self-adhesive material such as EVA (ethylenevinyl acetate) resin
or an adhesive made of an acrylic resin in a solvent, applying the
solution as a thin film on a cover film and then drying under warm
air, curing by UV rays or curing by electron beam the applied thin
film.
Of course, the above cover film can be used not only for preparing
a color filter but also for preparing another optically functional
film.
A photosensitive resin must also weakly adhere to the first
supporting substrate. Herein, it can be glued to the supporting
substrate utilizing self-adhesiveness of the photosensitive
resin.
When laminating a layer made of a photosensitive resin 391 on a CF
base 393, they are pressed with a pressure of 2 kg/cm.sup.2 while
heating both or one of the sides facing each other in the layer
made of the photosensitive resin 391 to 60.degree. C. During the
process, the metal roll must be heated by an appropriate method
such as electromagnetic induction so as to evenly heat the layer
made of the photosensitive resin 391. Furthermore, a pressure must
be evenly applied. Thus, it is desirable to apply a linear pressure
from a gap between a pair of rolls. Herein, the roll may be heated
by heating one or both of the pair of rolls for conducting heat
from the roll(s).
Since a layer made of a photosensitive resin 391 is laminated on a
CF base, it is desirable to block oxygen during exposure and to
form an oxygen blocking film made of silicon oxide or alumina to a
film thickness of 10 nm to 50 nm when using a polymer resin film as
the CF base. The oxygen blocking film is equivalent to a gas
barrier film in a base film, which is not limited to a silicon
oxide or alumina film. For an inorganic material such as silicon
oxide and alumina, a film thickness is preferably 10 nm to 50 nm. A
film thickness of 10 nm or more is adequate to block oxygen while a
thickness of 1 .mu.m or less does not lead to a particular problem
in manufacturing.
Furthermore, for avoiding damage on the layer made of a
photosensitive resin 39 during lamination, it is preferable to form
an excoriation-resistant protective film made of a polyester or
polyethylene resin for a CF base made of a polymer resin. A film
thickness may be within a range of 10 .mu.m to 200 .mu.m, and a
film having a thickness of 10 .mu.m or more may have adequate
excoriation resistance, resulting in no damage on the
photosensitive resin 391. A film thickness of 200 .mu.m or less may
not lead to a particular problem in manufacturing.
It is, of course, preferable to form a protective film not only for
manufacturing a color filter but also for improving excoriation
resistance during lamination.
An oxygen blocking film made of silicon oxide can be formed by, for
example, a continuous CVD apparatus. An oxygen blocking film made
of alumina may be formed by a continuous PVD apparatus.
Exposure may be satisfactorily conducted by a method using a common
extra-high voltage light as a light source such as contact exposure
and reduced projection exposure. A laser apparatus may be used as a
light source for reduced projection exposure. After development,
the polymer resin in the photosensitive resin 391 is crosslinked by
overheating or UV-ray irradiation.
Thus, the photosensitive resin becomes stable while its
adhesiveness to the CF base is improved.
Then, a red filter is formed on the CF base 393 comprising the
black matrix as described above. Subsequently, in a similar manner,
a green and a blue filters are formed to provide a color filter
layer 399 on the CF base (see, FIG. 12). This is just an example,
but the order of the colors can be determined as appropriate.
When the resin can be in a continuous process applied on the base
film, dried and laminated on the CF base or when using a
manufacturing apparatus capable of conducting such a continuous
process, the cover film 392 may be omitted.
A manufacturing apparatus comprises a wind-off roll and a wind-up
roll within it, and processes a film fed from the wind-off roll.
Its inside is shielded from the outer atmosphere and preferably has
a cleanliness factor of at least 1000 or less (a density of dusts
with a size of 0.1 to 0.5 .mu.m or less is 1000/m.sup.3 or less).
Furthermore, the inside is more preferably under an atmosphere of
an inert gas such as nitrogen, helium and argon.
The color filter may comprise a spacer on the black matrix. Herein,
as shown in FIG. 12, all of R (red), G (green) and B (blue)
constituting the color filter may be formed as described above,
before forming a spacer.
A spacer may be formed as a cylinder or prism as described for the
color filter. Its position on the black matrix may be inside of the
black matrix. In the light of an alignment margin, the spacer is
preferably designed to be at a position inside of the maximum
misalignment. A preferable height is 3 .mu.m to 5 .mu.m.
The color filter layer 399 formed on the CF base 393 is transferred
onto a functional film comprising a TFT layer 381 where a TFT
device, an interconnection and a pixel electrode are formed on a
base film 380, which is drawn from the wind-off roll to the wind-up
roll as shown in FIG. 13.
In FIG. 13, the CF base in the color filter 399 is peeled, after
which the color filter 399 is transferred to the TFT layer 401 via
the cover film 392 by a transfer roller. After the transfer, the
cover film 392 is peeled off.
In FIG. 13, assuming that the spacer 398 is formed on the side
which contacts with the cover film 392 and the color filter 399,
the side without a spacer in the color filter 399 is involved in
the transfer to the TFT layer. When no spacers 398 are formed, the
color filter 399 may be transferred to the TFT layer 401 on the
side which contacts with the cover film.
The cover film 392 may be, without being peeled, wound into a
wind-up roll together with the base film.
Although there has been described a configuration where the color
filter layer formed on the CF base 393 is transferred, the layer
may be laminated with the CF matrix base 393 using a base film.
Since the first supporting substrate 390 is peeled in addition to
the cover film 392, the photosensitive resin 391 and the color
filter layer 399 must be weakly adhesive to the substrate like the
cover film.
Although a photosensitive resin is used in this example, a colored
resin may be used. When using a colored resin, on a colored resin
is applied a photoresist, which is then exposed, developed, dried
and subjected to etching for removing an unnecessary colored layer
(not shown).
There will be an ink-jet type color filter as Example 5.
EXAMPLE 5
Ink-Jet Type
A color filter can be prepared, for example, by an ink-jet process
as follows.
Examples of a resin material used for forming a color filter layer
include, but not limited to, polyimide resins, PVA derivative
resins and acrylic resins. For example, in terms of an acrylic
resin, suitable resins are those with a molecular weight of about
5.times.10.sup.3 to 100.times.10.sup.3 prepared using about 3 to 5
monomers selected from alkyl acrylates or alkyl methacrylates such
as acrylic acid, methacrylic acid, methyl acrylate and methyl
methacrylate; cyclic acrylates and methacrylates; and hydroxyethyl
acrylate and methacrylate.
A diluting monomer may be, if necessary, added for adjusting
properties such as viscosity and curability of a color filter
layer. Examples of a diluting monomer include bifunctional monomers
such as 1,6-hexanediol diacrylate, ethyleneglycol diacrylate,
neopentylglycol diacrylate and triethyleneglycol diacrylate;
trifunctional monomers such as trimethylolpropane triacrylate,
pentaerythritol triacrylate and tris(2-hydroxyethyl)isocyanate; and
multifunctional monomers such as
di(trimethylolpropane)tetraacrylate and di(pentaerythritol)penta-
and hexa-acrylates. A suitable content of the diluting monomer is
about 20 to 150 parts by weight to 100 parts by weight of the
acrylic resin.
Examples of a pigment used for preparing a colored composition
include organic dyes, i.e., red pigments such as C. I. Nos. 9, 19,
81, 97, 122, 123, 144, 146, 149, 168, 169, 177, 180, 192 and 215,
green pigments such as C. I. Nos. 7 and 36, blue pigments such as
C. I. Nos. 15:1, 15:2, 15:3, 15:4, 15:6, 22, 60 and 64, purple
pigments such as C. I. Nos. 23 51319 and 39 42555:2, yellow
pigments such as C. I. Nos. 83, 138, 139, 101, 3, 74, 13 and 34,
black pigments such as carbon, and body pigments such as barium
sulfate, barium carbonate, alumina white and titanium.
A dispersing agent used for preparing a colored composition may be
a surfactant, a pigment intermediate, a dye intermediate or
Solsperse. Suitable examples of an organic dye derivative include
azo, phthalocyanine, quinacridone, anthraquinone, perylene,
thioindigo, dioxane and metal complex salt derivatives. The organic
dye derivatives are appropriately selected from those having a
substituent such as hydroxy, carboxyl, sulfone, carboxamide and
sulfonamide which exhibit good dispersibility.
A content of the pigment is about 50 parts by weight to 150 parts
by weight to 100 parts by weight of an acrylic resin. A content of
a dispersing agent is about 1 part by weight to 10 parts by weight
to the pigment. For adjusting spectral properties of a color
filter, a suitable pigment may be added as appropriate.
A thermal crosslinking agent used for preparing a colored
composition may be a melamine resin or an epoxy resin. Examples of
a melamine resin include alkylated melamine resin such as a
methylated melamine resin and a butylated melamine resin and mixed
etherated melamine resins, which may be of a high-condensation type
or a low-condensation type.
Examples of the above epoxy resin include glycerin, polyglycidyl
ether, trimethylolpropane polyglycidyl ether, resorcinol diglycidyl
ether, neopentylglycol diglycidyl ether, 1,6-hexanediol diglycidyl
ether and ethyleneglycol(polyethyleneglycol) diglycidyl ether.
A content of a thermal crosslinking agent is suitably 10 to 50
parts by weight to 100 parts by weight of an acrylic resin.
Suitable examples of a solvent used for preparing a colored
composition include toluene, xylene, ethyl cellosolve, ethyl
cellosolve acetate, diglyme, cyclohexanone, ethyl lactate and
propyleneglycol monomethyl ether acetate which may be used alone or
in combination of two or more, depending on a monomer composition,
a particular thermal crosslinking agent and a diluting monomer.
A colored composition used for forming a color filter layer
comprises a resin, a pigment, a dispersing agent, a thermal
crosslinking agent and a solvent as described above. The colored
composition is prepared as follows. First, an acrylic resin and a
pigment are kneaded using three rolls into chips, to which are then
added a dispersing agent and a solvent to prepare a paste. To the
paste are added a thermal crosslinking agent and a diluting monomer
to prepare an application solution of a colored composition.
On a supporting substrate are applied the application solutions of
black (black matrix), red, green and blue in a predetermined
pattern by an ink-jet process. Ink-jet apparatuses may be
classified into a piezo conversion system or a heat conversion
system, based on difference in an ink discharge system. In
particular, a piezo conversion system is suitable. Preferred is an
apparatus with an ink atomizing frequency of about 5 to 100 KHz and
a nozzle diameter of about 1 .mu.m to 80 .mu.m, having four heads,
each of which has 1 to 1,000 nozzles.
The number of heads may vary depending on the number of colors to
be applied. When three colors, i.e., red, green and blue, are
applied, three heads are used. Preferably, the number of heads are
at least equal to the number of colors applied and each head is
assigned to each color.
Before applying the solution on the supporting substrate by an
ink-jet process, an underlying layer matching a resin and/or a
solvent in the application solution may be formed for adjusting ink
receptivity and wettability in advance. The underlying layer may be
made of a polyimide resin, a PVA derivative resin, an acrylic resin
and/or an epoxy resin composition, to which porous particles of
silicon oxide or alumina may be added. A matrix light-shielding
layer may be formed by a photolithographic method or the above
transfer method, which may be conducted before or after forming the
color filter layer by an ink-jet process.
If necessary, over the color filter layer may be formed an overcoat
layer, which is used for improving apparent flatness, durability
represented by moisture resistance and chemical resistance in the
color filter layer, and for ensuring barrierhood for preventing
elution from the color filter layer. Examples of a material
suitably used include transparent resins such as thermosetting
acrylic copolymers containing maleimide and epoxy resin
compositions. The color filter formed on the supporting substrate
can be transferred to a functional film as described for a film
type color filter.
When forming the overcoat layer before transfer, the transfer may
be conducted on the side opposite to the overcoat surface in the
color filter as described for the film type filter.
Although the color filter layer was formed on the supporting
substrate in this example, the solution may be directly applied on
a functional film by an ink-jet process. Here, the color filter
layer is dried on the functional film, so that a color filter can
be formed on the functional film. By forming a cover film on the
color filter layer, deterioration of the color filter during
storage can be avoided. As described for the case where a color
filter is formed on a supporting substrate, an overcoat layer may
be formed over the color filter layer.
There will be detailed a light collector array and a rear emitting
light source comprising the light collector array as Example 6 of
this invention with reference to the drawings.
FIG. 30 is a schematic cross-sectional view of a rear light source
according to this example.
An optical guide 701 is an acrylic resin type film with a film
thickness of 300 .mu.m containing 20% by weight of silica with the
maximum particle size of 100 nm and an average particle size of 50
nm.
There is formed a light collector array on an optical guide 701. On
the light collector array, there is formed a light diffusing film
704.
A light diffusing film 704 has a film thickness of 40 .mu.m and
contains 25% by weight of an inorganic fillers consisting of silica
with an average particle size of 2 .mu.m and the maximum particle
size of 10 .mu.m. It is an acrylic resin type film as described for
the optical guide 701.
For color display, a rear light source in a liquid crystal must be
a white light and a light source 705 is an array of light-emitting
diodes 706 emitting R (red), G (green) and B (blue) (see, FIG.
30B). Although three primary colors are used in this example, two
colors which are mutually a complementary color, for example, blue
and yellow may be used or a white light-emitting diode may be
used.
When the optical guide 701 is so thin, specifically thinner than
the light-emitting diode in the light source, light can be focused
and guided to the optical guide 701 by a well-known method.
When a reflection film 702 is formed in a surface facing the light
collector array of the optical guide 701, a light from the light
source can be efficiently utilized. The reflection film 702 is an
aluminum thin film with a thickness of 10 .mu.m. There are no
particular restrictions to a film thickness, but the upper limit
may be generally 20 .mu.m in the light of limits of a weight and a
thickness. With the lower limit of 1 .mu.m or more, it may act as a
reflection film.
In this example, a light is collected into the light collector
array 703 (only one array is shown in FIG. 30C) formed in the in
the outgoing face of the optical guide 701 and then is taken
utilizing total reflection as shown in FIG. 30C. Thus, a reflection
film 702 is not essential, but in terms of reuse of a reflection
light in an interface, the light can be efficiently used by forming
a reflection film in the rear surface of the optical guide.
The light collector may have a variety of shapes as shown in FIG.
31, but it must be formed such that an area of the surface
contacting with the optical guide in the light collector is smaller
than an area of the surface facing the above surface in the light
collector.
In addition to the shape shown in FIG. 31, the light collector may
preferably have a cross-sectional shape such as an arc, a parabola,
an ellipse, a part of a trapezoid and a combination thereof.
Furthermore, in view of adhesiveness to the optical guide, its top
is preferably flat.
FIG. 32 is an overhead view of a light collector array. In the
light collector, "b" is preferably 10 .mu.m to 100 .mu.m both
inclusive, more preferably 20 .mu.m to 70 .mu.m both inclusive.
When it is 10 .mu.m or more, no interference fringes are formed in
a liquid crystal. When it is 100 .mu.m or less, a light efficiency
is not reduced.
There are no restrictions to the dimension "a", but it is generally
500 .mu.m to 10 .mu.m because no defects are generated during
manufacturing a light collector array and defective transfer can be
prevented during transfer.
A thickness is b/3 or more. For reducing a film thickness, the
dimension "b" in the light collector is preferably 20 .mu.m to 60
.mu.m both inclusive. When the dimension "b" in the light collector
is 20 .mu.m to 60 .mu.m both inclusive, the light collector can be
formed to a thickness of 7 .mu.m to 20 .mu.m.
In this example, a light collector with a=200 .mu.m, b=50 .mu.m and
a thickness of 10 .mu.m is used.
Thus, a rear-emitting light source could be formed to a thickness
of 350 .mu.m (0.35 mm). In other words, a thickness could be
reduced in comparison with 0.8 mm in a conventional optical guide.
In a conventional optical guide, a larger optical guide requires a
larger film thickness, whereas in this invention, increase in a
dimension does not lead to a larger film thickness of the optical
guide. Furthermore, in a rear-emitting light source of this
invention, a flexible thin film can be used in an optical guide, so
that impact resistance can be also significantly improved.
Next, there will be described a process for manufacturing a light
collector array. A light collector array can be prepared by coating
a female die with a resin, curing the resin while pressing the
supporting film from the resin side and releasing the cured resin
from the female die (FIG. 33), or alternatively, by coating a base
film with a resin, curing the resin while pressing the resin side
against a female die and releasing the cured resin from the female
die (FIGS. 34, 35). As will be detailed later, UV rays can be
irradiated from the rear side of the supporting film 708 (see, FIG.
34), or alternatively from the side of the female die (FIG.
35).
A thermosetting resin may be used in place of a UV cure resin 709.
However, since only a part pressed by the female die should be
heated, it is preferable to use a UV cure resin.
In such a case, curing of the resin does not have to completely
proceed, but may be to a degree such that a pattern shape can be
retained.
A resin for pattern curing which can be used may be, for example, a
resin which can be cured by an active energy ray or heating.
In this example, the use of an acrylic resin as described for a
base film is illustrated, but a resin used is not limited to an
acrylic resin.
When a light collector is made of a material as described for the
optical guide light collector, a light efficiency is improved
because a refractive index is substantially equivalent in the
optical guide and the light collector so that a light is not
reflected in an interface between the optical guide and the light
collector.
An active energy ray used for curing is preferably UV rays.
Examples of a lamp generating UV rays include a metal halide type
lamp and a high-pressure mercury-vapor lamp.
In curing with an active energy ray such as UV rays, preferably a
photopolymerization initiator which generates radical is added.
Examples of a photopolymerization initiator used here include
benzophenone, benzoin methyl ether, benzoin propyl ether,
diethoxyacetophenone, 1-hydroxy-cyclohexyl phenyl ketone,
2,6-dimethylbenzoyl-diphenylphosphine oxide,
2,4,6-trimethylbenzoyl-diphenylphosphine oxide and benzophenone.
Two or more of these photopolymerization initiators may be
combined. A content of a photopolymerization initiator is
preferably 0.01 to 2 parts by weight to 100 parts by weight of an
organic component having a (meth)acryl group. A too low content may
lead to insufficient sensitivity to complete curing while a too
high content may lead to excessive sensitivity which may cause a
curing reaction during compounding, resulting in defective
application.
In thermal polymerization, a thermal-polymerization initiator may
be added as necessary. Examples of a thermal-polymerization
initiator used here include benzoyl peroxide, diisopropyl
peroxycarbonate and t-butyl peroxy (2-ethylhexanoate), which can be
used an amount of 0.01 to 1 parts by weight to 100 parts by weight
of an organic component having (meth)acryl group.
When a UV-ray cure resin is used and the film has a high
transmittance to a wavelength curing mainly the UV-ray cure resin,
UV rays may be irradiated from the film side (FIG. 34). When the
film has a low transmittance to the wavelength, the female die can
be formed by using a transparent material which is transparent to
the wavelength and UV rays may be irradiated from the female die
side (FIG. 35).
When using a film comprising light-scattering particles, the light
diffusing film may be a single film as shown in FIG. 36, or a
laminated film as shown in FIGS. 37 and 38. In FIG. 37, the light
diffusing film is formed just over the light collector array. In
FIG. 38, the light diffusing film is formed on a supporting film.
Any of the configurations shown in FIGS. 36 to 38 may be
employed.
Next, there will be described a process for manufacturing a rear
light source having the configuration shown in FIG. 31. A light
collector array is formed on a supporting film as described for
FIGS. 33 to 35. Then, the light collector array is transferred on a
base film to be an optical guide. For a supporting film endowed
with light scattering function, the supporting film with the array
can be laminated.
In terms of a reflection film, a reflection film made of, for
example, a metal (e.g., aluminum) is preliminarily formed on a
surface facing the surface in the base film to be an optical guide
on which a light collector array is to be formed, to a film
thickness of 10 .mu.m. A functional film on the reflection film can
be formed as described in Example 8 and therefore will not be
described in detail.
FIG. 39 shows a schematic cross-sectional view of a liquid crystal
structure comprising the light collector array thus obtained.
FIG. 40 shows that without being cut, an uncut sheet of base film
is laminated to form a plurality of liquid-crystal panels on the
base film, which are then cut into individual liquid-crystal panels
by precise cutting.
Since a process for manufacturing a liquid-crystal panel in FIG. 40
is as described above, it will not be described in detail.
After laminating the optical guide with the liquid crystal cell,
the film can be precisely cut in accordance with a size of each
liquid crystal display device (FIG. 40), or the liquid crystal cell
can be cut into a particular number of pieces, which is then
precisely cut in accordance with a display size (FIG. 41).
Alternatively, after the liquid crystal cell is cut into a
particular number of pieces, they can be laminated with the optical
guide (FIG. 42).
Cutting in this process may be conducted by, for example, cutting
by laser beam scanning or punching by a Thomson blade. For
obtaining a liquid-crystal panel by precise cutting, it is
necessary to cut over a sealing material. A width of the liquid
crystal sealing material is desirably 2 mm or more. A width of less
than the range may cause defects such as detachment during cutting.
It is desirably 3 mm or more.
There are no particular restrictions to the upper limit of a
cutting margin. However, a too large margin may cause problems such
as a larger loss and a larger panel area. The upper limit may be,
therefore, generally about 5 mm.
Even when using a light collector as a rear light source, a
liquid-crystal panel comprising a rear light source with a
thickness of about 470 .mu.m could be prepared. Although a film
with a thickness of 300 .mu.m was used as an optical guide in this
example, an optical guide with a film thickness of 200 .mu.m was
prepared with no problems. Here, a film thickness of the
liquid-crystal panel was about 370 .mu.m.
There will be described a configuration of an organic EL device as
Example 7.
A light-emitting layer comprises a single layer or multiple layers
made of an organic compound or a complex with a thickness of
several ten nanometers to several hundred nanometers comprising a
light-emitting layer. In comparison with the single-layer
structure, the appropriately combined multiple-layer structure
improves a binding efficiency between an electron and a hole in the
light-emitting layer and thus a combined excitation energy improves
a light-emitting efficiency.
A light-emitting layer has, for a three-layer structure, a
configuration comprising a hole transport layer efficiently
transporting holes which is in contact with an anode electrode
(anode), a light-emitting layer containing a light-emitting
material and an electron transport layer efficiently transporting
electrons which is in contact with a cathode electrode (cathode).
In addition, there may be appropriately disposed a lithium fluoride
layer, a layer of an inorganic metal salt and/or layers comprising
thereof.
In the above description, a light-emitting layer and a hole or
electron transport layer may have, besides a single layer
configuration, a multiple layer configuration for providing white
light emission and efficient transportation of holes or electrons,
respectively.
For using as a backlight for a liquid crystal, a light emitted from
an organic EL device should be white (for example, daylight
standard light source D65 (color temperature: 6500 K)). However, to
date, there are no single light-emitting materials which can emit a
white light. A white light is, therefore, emitted by coincidentally
producing, from a plurality of light-emitting material, a plurality
of colored lights, which are then combined. A combination of
multiple colored lights may be that containing three light maximum
wavelengths of three primary colors, i.e., blue, green and blue, or
alternatively that containing two light maximum wavelengths
utilizing complementary color system such as blue and yellow and
blue-green and orange, but the emitted light should be suitable for
a spectral transmittance in each color filter.
Light emission from an organic EL involves utilizing a fluorescence
from an organic material or exciting an organic material as a
light-emission host and then utilizing a phosphorescence dopant
which emits a phosphorescence by transition between the excited
state and a spectral term with a different multiplicity. To date,
no single materials capable of emitting a phosphorescence have been
found. However, an organic material capable of emitting a
phosphorescence alone can be, of course, used.
A white light may be obtained from a combination of these
fluorescence-emitting organic materials, a pair of
phosphorescence-emitting organic materials and a pair of a
fluorescence-emitting organic material and a
phosphorescence-emitting organic material.
There are no particular restrictions to a combination of materials
for a light-emitting layer for obtaining a white light, and they
may be combined such that a wavelength range matches a spectral
transmittance in each color filter. In particular, when utilizing a
phosphorescence, examples of a light-emission host include
materials containing, as a motif, a partial structure such as
carbazole derivatives, biphenyl derivatives, styryl derivatives,
benzofuran derivatives, thiophene derivatives, arylsilane
derivatives. Among others, carbazole derivatives and biphenyl
derivatives are preferable light-emitting materials exhibiting a
higher light-emission efficiency.
When forming a hole transport layer, there are no restrictions to a
material as long as it can transport holes from an anode to a
light-emitting layer. Thus, it may be appropriately selected from
those commonly used as a charge-injection material for holes in a
photoconductive material and known materials used for a hole
transport layer in an EL device.
When forming an electron transport layer, there are also no
particular restrictions to a material. The material may be
appropriately selected from well-known materials capable of
transporting electrons from a cathode to a light-emitting
layer.
A light-emitting layer can be formed by any of known methods for
forming a film such as vacuum deposition, spin coating, casting,
spraying, ink-jet application, painting and printing.
A reflection film preferably has a reflectance of at least 60% for
efficiently reflecting a light from a light-emitting layer or an
outside light.
A transparent electrode layer is made of a metal material with a
thickness of several tens nanometers to several hundred nanometers
having a transmittance of 60% or more for reducing loss of a
transmitting outside light or light from a light-emitting
layer.
A metal material used as an anode may be appropriately selected
from known metals, metal oxides, alloys, electrically conductive
compounds and mixtures thereof. A material having a work function
of 4 eV or more may be, however, preferably used because holes can
be efficiently injected into the light-emitting layer.
Examples of an anode material include metals such as Au; and
conductive materials such as CuI, indium tin oxide (ITO), indium
zinc oxide (IZO), SnO.sub.2 and ZnO.
When an anode is light-reflective, an anode with a high reflectance
may be a laminate of the above material and a metal material with a
high reflectance such as aluminum. For example, an anode may be a
laminate of ITO/aluminum in sequence from the light-emitting layer.
Alternatively, an aluminum film may be formed as a reflection film,
with which an ITO is laminated via an insulating film such as an
oxide film to form an anode.
A metal material used as a cathode may be appropriately selected
from known metals, alloys, electroconductive compounds and mixtures
thereof. A material having a work function of 4 eV or less may be,
however, preferably used because electrons can be efficiently
injected into the light-emitting layer.
Examples of a metal material for a cathode include sodium,
sodium-potassium alloys, magnesium, lithium, magnesium/silver
mixtures, magnesium/aluminum mixtures, magnesium/indium mixtures,
aluminum, aluminum/aluminum oxide mixtures and rare-earth
metals.
When a transparent electrode is used as a cathode, it can be formed
by laminating a cathode material film with an anode electrode
material with a high transmittance. For example, a transparent
cathode can be formed by sequentially laminating an aluminum
film/ITO from the light-emitting layer.
Both cathode and anode are formed by, for example, vapor deposition
or sputtering. Alternatively, an electrode may be formed by
dispersing an electroconductive compound with an appropriate binder
resin and applying the dispersion.
An electrode pattern may be formed by forming an electrode and then
patterning it into a desired shape by photolithography, or by using
a mask having an opening with a desired shape during vapor
deposition or sputtering.
Next, there will be described specific manufacturing a
light-emitting layer in an organic EL device. The structural
formulae of materials PVK, Ir6, Ir12, CBP, (NPD, BC and Alq3 used
in the manufacturing are as follows:
##STR00015##
##STR00016##
##STR00017##
##STR00018##
##STR00019##
##STR00020##
##STR00021##
An organic EL device with configuration 1 utilizes a polymer
material PVK as a light-emission host, Ir6 as a phosphorescence
dopant and a phosphorescence of Ir12. This is a top emission type
device having two light-emission maximum wavelengths, from Ir6
having a maximum wavelength in a red range and Ir12 having a
maximum wavelength between a green and a blue ranges, but
embodiments of an organic EL device are not limited to this.
First, a surface of a base film on which an organic EL device is to
be formed was etched by oxygen plasma. Next, on the etched base
film were sequentially deposited aluminum to 100 nm and ITO to 50
nm by sputtering and a metal anode electrode to be a reflection
electrode layer. Subsequently, on the reflection electrode layer
was applied a PEDOT/PSS solution (polyethylene
dioxythiophene-polysulfonic acid dopant; baytron from Bayer AG) to
100 nm by printing, to form a hole transport layer. After drying by
heating, on the layer was applied a solution of 30 mg of PVK as a
light-emission host, 0.2 mg of the phosphorescence dopant Ir6, 2.0
mg of the phosphorescence dopant Ir12, 2 mg of an
electron-transporting material
2-(4-biphenylyl)-6-(4-t-butylphenyl)1,3,4-oxadiazole (OXD) in 2 mL
of dichloromethane to a film thickness of 100 nm by printing to
form a light-emitting layer, which was then dried by heating.
Then, using a stainless steel mask having an opening with a given
electrode shape, lithium fluoride was deposited to a film thickness
of 0.5 nm by sputtering. By sputtering were aluminum to 10 nm and
ITO to 100 nm, to form a transparent cathode as a transparent
electrode layer.
The materials used for forming an organic EL device with
configuration 2 were CBP, Ir6, Ir12, (NPD, BC and Alq3.
The organic EL device of this configuration is of a bottom emission
type emitting a light having two emission maximum wavelengths which
utilizes a low-molecular weight material CBP as a light-emission
host, a phosphorescence dopant Ir6 and phosphorescence of Ir12.
However, embodiments of an organic EL device are not limited to
this.
First, a surface of a base film on which an organic EL device is to
be formed was etched by oxygen plasma. Next, on the etched base
film was deposited ITO to a film thickness of 100 nm to form a
transparent anode electrode to be a transparent electrode layer.
Then, using a stainless steel film plate having an opening of 100
mm.times.100 mm for masking, (NPD was deposited to a film thickness
of 20 nm at a deposition rate of 0.5 nm/s by resistance heating of
vacuum deposition under an atmosphere of vacuum at 10-4 Pa to form
a hole transport layer. Subsequently, using a mask, on the hole
transport layer were co-deposited, by resistance heating, CBP as a
light-emission host, the phosphorescence dopant Ir6 and the
phosphorescence dopant Ir12 at vapor deposition rates of 0.5 nm/s,
0.005 nm/s and 0.02 nm/s, respectively to a film thickness of 30
nm, to form a light-emitting layer. Then, on the light-emitting
layer were vapor deposited BC at a vapor deposition rate of 5
.ANG./s to a film thickness of 10 nm by resistance heating using a
mask and then Alq3 at a vapor deposition rate of 5 .ANG./s to a
film thickness of 40 nm to form a laminated electron-transport
layer.
Next, using a stainless steel mask having an opening with a given
electrode pattern shape, on the layer were sequentially deposited
lithium fluoride at a vapor deposition rate of 0.01 nm/s to a film
thickness of 0.5 nm and aluminum at a vapor deposition rate of 1
nm/s to a film thickness of 100 nm by resistance heating, to form a
metal cathode as a counter-electrode layer.
There will be described assembling of a panel as Example 8 of this
invention.
EXAMPLE 8
Assembling a Panel
An optically oriented film was formed as follows:
##STR00022##
To 99 parts by weight of a compound represented by formula (12) was
added 1 part by weight of a photopolymerization initiator
"Irgacure-651" (Ciba-Geigy), and the mixture was dissolved in
dimethylformamide to prepare a 5% solid solution. The solution was
filtrated with a 0.1 .mu.m filter to obtain an optically oriented
material solution.
This solution was evenly applied on each of functional films A and
B cut from the roll by a flexographic press, and dried at
100.degree. C. for 15 min. The coating film thus formed was
irradiated with linearly-polarized UV rays at a wavelength of about
365 nm to an accumulative light amount of 30 J/cm.sup.2 from a
extra-high pressure mercury lamp, for optical orientation. Next,
the same surface was irradiated with non-polarized UV rays at a
wavelength of about 313 nm to an accumulative light amount of 50
J/cm.sup.2 from a extra-high pressure mercury lamp to initiate
polymerization of the optically oriented material.
An oriented film with a thickness of 0.02 .mu.m was obtained.
Subsequently, there will be described lamination using a sealing
material.
For the purpose of synthesizing a sealing material, in a reaction
vessel equipped with a nitrogen gas inlet tube, a stirrer and a
reflux condenser were 500 parts of a carboxyl-containing diol,
Placcel-205BA (Daicel Chemical Industries Ltd.: a number average
molecular weight=500), 444 parts of isophorone diisocyanate, and
then 0.1 parts of tin octoate, and the mixture was reacted at
60.degree. C. for 1 hour. Then, to the mixture were added 260 parts
of 2-hydroxypropyl acrylate, 0.4 parts of t-butylhydroquinone as a
polymerization inhibitor and 0.2 parts of tin octoate as a
catalyst, and then the mixture was reacted at 70.degree. C. for 11
hours, to prepare a carboxyl-containing urethane acrylate with
0.05% of the residual isocyanate.
In a reaction vessel were placed 18 parts of PTG-850 (Hodogaya
Chemical Co., Ltd.: polytetramethyleneglycol with a number average
molecular weight of 850), 9.8 parts of maleimide caproate, 1.2
parts of p-toluenesulfonic acid, 0.06 parts of
2,6-tert-butyl-p-cresol and 15 parts of toluene, and the mixture
was reacted with stirring for 4 hours under the conditions of 240
torr and 80.degree. C., while removing water generated.
The reaction mixture was dissolved in 200 parts of toluene and the
resulting solution was washed with 100 parts of a saturated sodium
bicarbonate solution 3 times and 100 parts of saturated saline 1
time. The organic layer was concentrated to provide a maleimide
derivative, i.e., polytetramethyleneglycol bis(maleimide
caproate).
In a flask were placed 55 parts of the carboxyl-containing urethane
acrylate, 5 parts of polytetramethyleneglycol bis(maleimide
caproate) described above, 5 parts of a silane coupling agent
KBM-803 (Shin-Etsu Chemical Co., Ltd.) and 40 parts of isobornyl
acrylate, and the mixture in the flask was melt-blended with
stirring at 80.degree. C. for 1 hour until no unmelted compounds in
the sample were present, to obtain a photocuring resin
composition.
The photocuring resin composition containing aluminum oxide balls
with a diameter of 3 .mu.m was applied desired parts of the
functional films A and B comprising the liquid crystal oriented
film (for example, an outer edge, an outer edge of each pixel
cell), which were disposed facing each other and then laminated.
The sealing material was cured by irradiation with UV rays to 500
mJ/cm.sup.2 from a metal halide lamp. Then, a desired liquid
crystal was injected and the injection port was sealed using the
photocuring resin composition as described above.
There will be described a specific example of preparing an oriented
film by rubbing.
A liquid crystal orienting agent was applied on a supporting film
using a printer for application of a liquid crystal oriented film,
and then dried on a hot plate at 150.degree. C. for 90 min, to form
a coating film with an average dry film thickness of 0.06 .mu.m.
The coating film was rubbed by a rubbing machine having a roll
wrapped with a rayon cloth under the conditions of a roll
revolution of 400 rpm, a stage travelling speed of 3 cm/sec and a
hair pushing length of 0.4 mm. After being washed with water, the
film was dried on a hot plate at 100.degree. C. for 5 min to obtain
an oriented film.
There will be described an active driving type liquid crystal
display panel as Example 9 of this invention.
FIG. 14 is a cross-sectional view of an active driving type liquid
crystal display panel according to this example.
FIG. 14 shows a semi-transmissive liquid crystal display panel as
described in terms of the prior art, except in contrast to FIG. 27,
a backlight unit is a backlight using a light-condensing film in
place of an LED light source and a glass substrate is a base
film.
A liquid-crystal panel unit comprises functional films, i.e., a
first, a second and a third functional films.
The first functional film has a configuration where a pixel
electrode 360, a device layer 375 consisting of an interconnection
and a thin-film transistor 361, and an oriented film are
transferred on a base film 362 as described above. The second
functional film has a configuration where a color filter 355, a
transparent electrode 356 and an oriented film 357 are transferred
on a base film 354 as described above. The third functional film
has a configuration where at least in a light collector film, a
light collector 366 and a supporting film 365 are transferred on a
base film 368.
The retardation film 363 and the polarizing film 364 may be formed
by transfer onto the transparent electrode 365 or onto the base
film 362.
There will be described a method for transferring functional thin
films to both sides of a base film with reference to FIG. 15.
On the device layer 375 formed on the base film 362 in the first
functional film 372 were transferred the oriented film 359 formed
on the second functional film 371. On the base film 362 in the
first functional film 372 was transferred an optically functional
thin film 376 consisting of a retardation film and a polarizing
film formed on the third functional film 377.
In FIG. 15, there are not formed a cover film over the first, the
second or the third functional film, but it may be formed. The
optically functional thin film 376 may be transferred on the matrix
base 373 in any order. As described above for FIG. 3, it may
transferred in the order according to the design.
The base film 362 in the configuration shown in FIG. 14 may be
omitted by sequentially transferring a light-condensing film, an
optically functional thin film, a pixel electrode and so forth on
the base film 368.
Although the above structure is similar to that of the prior art
shown in FIG. 14, a flexible base film is used as a substrate, so
that the substrate may be thinner and softer. Thus, an impact can
be absorbed by flexion of the substrate, resulting in significant
improvement in impact resistance. The pixel electrode in FIG. 14 is
semi-transparent and its surface has an irregularity by the prior
art.
There will be detailed the active driving type liquid crystal
display panel of Example 9 with reference to the drawings.
FIG. 16 is a cross-sectional view for describing a configuration of
an active driving type liquid crystal display panel according to
this invention. The active driving type liquid crystal display
panel of this example has a configuration where a liquid crystal is
sandwiched between a second functional film comprising a backlight
and a first functional film comprising thin-film transistor as
shown in the bottom part of FIG. 16. A thickness of both of the
second functional film comprising a backlight and the first
functional film comprising a thin-film transistor is about 0.2
mm.
As shown in FIG. 16, the first functional film comprises, in one
surface of a plastic substrate (base film) to be a supporting
substrate, a thin-film transistor circuit 402, a pixel electrode
403, a color filter 404 consisting of red, green and blue, a spacer
A and an oriented film 405. In the other surface, a
linearly-polarized light film and a retardation film are formed
(not shown). Furthermore, the spacer may be suitably formed in the
second functional film.
The second functional film B comprises a light collector 412, a
supporting film 411, a reflection electrode 413, a polarizing film
410, a retardation film 409, a transparent counter electrode 408
facing the pixel electrode 403 in a liquid crystal device and an
oriented film 407, where the oriented film 405 formed on the first
functional film and the oriented film 407 formed on the functional
film B are disposed facing each other and a liquid crystal 406
fills the space between them.
In the surfaces of the backlight and the functional film which is
in contact with a liquid crystal, there is formed an oriented film
for orienting the liquid crystal to a desired direction and a
spacer A is provided in the lower side of the black matrix for
keeping a distance between them constant.
A pitch of pixel electrodes in FIG. 16 depends on a resolution of
the active driving type liquid crystal display panel. For example,
for an active driving type liquid crystal display panel comprising
three color filters of R (red), G (green) and B (blue) with a
resolution of 200 ppi (pixEL per inch), a pitch of pixel electrodes
is 25400 .mu.m/200/3=42.3 .mu.m.
The various layers in FIG. 16 may be formed with a film thickness
as follows. The transparent electrode, the counter electrode and
the pixel electrode comprises an ITO film with a thickness of 0.1
.mu.m to 0.2 .mu.m. The thin-film transistor and the
interconnection are a polysilicon film and a metal film (generally,
aluminum or an aluminum alloy), respectively, with a thickness of
0.1 .mu.m to 0.2 .mu.m. The backlight unit comprising a
light-condensing film has a thickness of 0.4 mm to 0.6 mm including
a thickness as a base film. The liquid crystal part has a thickness
of 2 .mu.m to 6 .mu.m. The retardation film has a thickness of 0.5
.mu.m to 10 .mu.m (conventionally, 100 .mu.m to 300 .mu.m). The
polarizing film has a thickness of 5 .mu.m to 50 .mu.m
(conventionally, 100 .mu.m to 250 .mu.m). The oriented film has a
thickness of 0.01 .mu.m to 0.2 .mu.m (conventionally, 0.04 .mu.m to
2 .mu.m). The color filter has a thickness of 1 .mu.m to 3 .mu.m
(conventionally, 100 .mu.m to 200 .mu.m).
In this example, the transistor layer, the color filter, the
polarizing film, the retardation film, the oriented film and the
liquid crystal part could be formed in 0.5 .mu.m, 2.5 .mu.m, 8
.mu.m, 7 .mu.m, 0.1 .mu.m and 6 .mu.m, respectively. The base film
used was an acrylic resin type film with a film thickness of 100
nm. The backlight used in the light-condensing film could be formed
in about 470 .mu.m. Thus, the liquid-crystal panel had a thickness
of about 490 .mu.m (0.49 mm) including the backlight. That is, the
liquid-crystal panel could be formed with a reduced film
thickness.
The liquid-crystal panel can be wounded-up into a roll with a
radius of 40 mm. Thus, a nonconventional liquid-crystal panel was
manufactured, which can be handled like a paper.
In this invention, film thicknesses of the color filter/the
retardation film/the polarizing film/the oriented film can be
significantly reduced in comparison with those in the prior art by
modifying a manufacturing process and/or materials. Thus, a
distance between the color filter and the reflection electrode can
be adequately small in relation to the pixel electrode pitch of
about 40 .mu.m. In this example, the distance was reduced to 15
.mu.m or less because the thicknesses were as follows: the liquid
crystal part (3 .mu.m), retardation film (3 .mu.m), polarizing film
(6 .mu.m) and oriented film (0.01 .mu.m).
As a result, in comparison with a semi-transmissive liquid crystal
display panel, a reflectance in the reflection film can be
comparable to a conventional reflective liquid crystal display
panel, and a liquid crystal display panel can be prepared, which
has a light efficiency of the backlight comparable to a
conventional transmissive liquid crystal display panel.
Specifically, a liquid crystal display structure comprising a
liquid crystal display panel of this example operates as a
reflective liquid crystal display in a bright place by reflecting
an outside light, while operating as a transmissive liquid crystal
display in a dark place, using a backlight. Thus, a light
efficiency can be improved in both outside light and rear light
source in comparison with a conventional semi-transmissive liquid
crystal display. Furthermore, in a bright place, it acts as a
reflective liquid crystal display, so that it can provide an image
comparable to a reflective liquid crystal display while in a dark
place, a backlight intensity can be reduced, compared with a
semi-transmissive liquid crystal display.
A liquid crystal display refers to a device displaying an image on
the basis of image data input from the outside (for example, a
device displaying an image on the basis of an image signal input
from the outside like a display for a personal computer). An
information terminal such as a television having display function,
a notebook type personal computer, a cell phone and a PDP is
distinguished from an electronic equipped with a liquid crystal
display.
By providing a surface of a display device with an apparatus for
monitoring an illumination intensity, a backlight can be OFF in a
bright place, which contributes reduction in power consumption. In
a mobile device driven by a battery such as a cell phone, a battery
life can be effectively increased.
Furthermore, since a distance between a color filter and a
reflection film can be adequately reduced in relation to an
electrode pitch, there can be provided a novel liquid crystal
display panel in which a light reflected by a reflection film does
not enter a filter of another color and thus a light efficiency is
not reduced.
There will be described a manufacturing process of this example
with reference to the drawings.
A process for manufacturing a functional film A will be described
with reference to FIG. 17. As shown in FIG. 17, first are prepared
a first film comprising a transistor layer 452 on a base film 451,
a second film comprising a color filter on a supporting film 453, a
third film comprising a spacer on a supporting film 453 and a
fourth film comprising an oriented film 456 on a supporting film
453. Then, the first film comprising the transistor layer is fed
from a wind-off roll to a wind-up roll. In the course of the
feeding, after peeling off the supporting film 453, a color filter
formed 454 on the second film is transferred onto the transistor
layer 452; then, after peeling off the supporting film 453, the
spacer 455 on the third film is transferred onto the color filter
454; and finally, after peeling off the supporting film, the
oriented film 456 on the fourth film is transferred onto the
spacer, to form a functional film A.
A functional film B is, although being not shown, prepared as
described for the functional film A. First, are prepared a fifth
film comprising a reflection electrode on a base film, a sixth film
comprising an organic light-emitting layer on a supporting film, a
seventh film comprising a transparent electrode on a supporting
film, an eighth film comprising a polarizing film on a supporting
film, a ninth film comprising a retardation film on a supporting
film and a tenth film comprising an oriented film on a supporting
film. Next, the fifth film comprising the reflection electrode is
fed from a wind-off roll to a wind-up roll. In the course of the
feeding, after peeling off the supporting film 453, the organic
light-emitting layer on the sixth film is transferred onto the
reflection electrode; then, the transparent electrode on the
seventh film is peeled off and transferred to the organic
light-emitting layer; and the polarizing film on the eighth film is
peeled off from the supporting film and transferred to the
transparent electrode. After transferring the transparent
electrode, a protective film for protecting an organic
light-emitting layer made of an organic material is deposited by
physical vapor deposition. The protective film may be made of an
organic material or a mixture of an organic and an inorganic
materials. Here, a protective film may be formed on a supporting
film and then deposited on a transparent electrode using a transfer
method described above.
Next, the phase difference formed on the ninth film is transferred
onto the polarizing film, a transparent electrode is deposited on
the retardation film by physical vapor deposition, the oriented
film on the tenth film is transferred onto the transparent
electrode to prepare a functional film B.
The oriented films formed on the functional films A and B are
placed facing each other such that they forms a given angle, and
then the space between the oriented films is filled with a liquid
crystal to prepare a liquid-crystal panel.
There will be described operation of the panel according to this
example with reference to FIG. 16.
First, there will be described operation as a transmissive liquid
crystal display panel. A white light emitted from a backlight 414
consisting of a base film 413 as an optical guide and a
light-condensing film 412 is non-polarized, but only one
linearly-polarized light passes through a polarizing layer 410, to
a liquid crystal layer 406. Here, an orientation state of liquid
crystal molecules is controlled by the presence or the absence of
an applied potential to the pixel electrode 403 as a transparent
electrode. That is, in an extreme orientation state, a
linearly-polarized light entering from the bottom of FIG. 16 passes
through the liquid crystal layer as it is. A light at a wavelength
within a particular range passes through the pixel electrode 403
consisting of the color filter 404 and the transparent electrode
and then substantially completely absorbed by the polarizing layer
400. Therefore, the pixel develops black.
In contrast, in another extreme orientation state, a polarization
state of a light passing through the liquid crystal layer 406 is
changed and a light passing through the color filter 404
substantially totally passes through the polarizing layer 400.
Therefore, this pixel most strongly develops a color determined by
a color filter. In an orientation state between these extremes, a
light partially passes through the layer, so that the pixel
develops an intermediate color.
Here, when the color filter material is electrically conductive, a
voltage applied to a transparent electrode in a pixel for applying
a given voltage to the liquid crystal can be reduced. Therefore,
the color filter material is desirably electrically conductive.
Next, there will be described a modification of Example 9 with
reference to the drawings. Although in modification 1 of Example 9,
a functional film A has a configuration that a thin-film transistor
circuit and a color filter are sequentially transferred to a base
film as shown in FIG. 16, a functional film prepared by
sequentially transferring a color filter and a thin-film transistor
may be used. FIG. 18 is a cross-sectional view showing a
configuration of modification 1. A difference from that in FIG. 16
is positional relationship between the thin-film transistor and the
color filter.
There will be described a configuration where a color filter is
disposed in the liquid crystal side of the transparent electrode in
the liquid crystal in the functional film 2 side where a backlight
is to be formed, as modification 2 of Example 9.
Although the color filters 404 are disposed in the liquid crystal
side in the functional film A in Example 9 and modification 1,
these may be disposed in the backlight side of the functional film
B. FIG. 17 shows modification 2 of Example 8. Difference from
Example 9 and modifications 1 and 2 is that the color filters 404
are disposed in the functional film in the backlight side and in
the liquid crystal side of the transparent electrode in the liquid
crystal device.
Although being not shown, the various modifications can be, of
course, prepared by the manufacturing process described in Example
10.
Although Example 9 shows coincidentally forming a backlight and a
liquid crystal device in a functional film, films having various
functions may be sequentially formed on a functional film. In
particular, a functional film B in the backlight side comprises an
organic EL device and a part of a liquid crystal device. Thus, the
film have many functions such as a reflection electrode, a
light-emitting layer, a transparent electrode, a sealing layer,
polarizing function and a transparent electrode, leading to a
longer manufacturing process. Continuous production using a
roll-to-roll system may be advantageous in a production efficiency.
However, since a pass rate in each production process is not 1, an
yield of the functional film B in the backlight side is
particularly reduced. For solving the problem, a plurality of film
substrates are used and functions to be provided are distributed
among these substrates instead of concentrating various functions
to a single film substrate. That is, it is desirable to increase an
yield by unitization.
There will be described forming an irregularity in a reflection
electrode as Example 10 of this invention.
This example essentially comprises the steps of forming an
irregularity on a substrate consisting of a base film or functional
film and then forming a reflection film. The reflection film formed
on the convexo-concave is provided as a diffuse reflection film by
(1) forming the reflection film with a metal thin film. Here, the
reflection film can be formed with a reduced film thickness or
partially formed to give a semi-transparent film by which a light
is transmitted/reflected in a desired ratio. (2) A desired
semi-transparent film made of an insulating material other than a
metal can be provided by making a refractive index difference
between media for forming a reflective polarizing film and a light
diffusing surface in place of using a metal film.
Transparency in a reflection film depends on a design of a liquid
crystal. Semi-transparency is sometimes required, and any
transparency is sometimes not required. When any transparency is
not required, the film can be designed to have a transmittance of
0%.
The reflection film may be made of a material appropriately
selected according to a wavelength range to be reflected; for
example, a metal exhibiting a higher reflectance in a visible-light
wavelength range of 300 nm to 800 nm, such as aluminum, gold and
silver can be formed by an appropriate method such as vacuum
deposition and sputtering. A known reflection-increasing film (see,
for example, Kogaku Gairon 2 (Compendium of Optical Science Vol.
II), Junpei Tsujiuchi, Asakura Book Co., 1976) can be deposited as
described above. A thickness of the reflection film is preferably
0.01 .mu.m to 50 .mu.m. Only a necessary part in the reflection
film may be patterned by, for example, photolithography or mask
vapor deposition. A function as a semi-transparent and
semi-reflective film can be controlled by adjusting a thickness of
the reflection film or a numerical aperture in patterning depending
on a desired transmittance.
Next, there will be described a light diffusing film providing a
light diffusing function by its surface irregularity, as well as a
method for forming an irregularity on the surface of the above
substrate by the light diffusing film.
The reflection film may be provided with an irregularity by forming
an energy-sensitive resin layer on a surface in the above substrate
where the irregularity to be formed, irradiating the
energy-sensitive resin layer with an active energy ray via a
patterned mask or by a direct drawing method and then removing the
exposed part or the unexposed part in the resin layer by a
developing solution; by forming a thin film layer on the surface in
which the irregularity to be formed and pressing a surface of a
transfer mold onto the thin film layer for transferring; or
alternatively, by depositing a thin film layer on a transfer mold
and then transferring the thin film layer to a surface where the
irregularity is to be formed.
First, there will be described a method for forming an irregularity
from an energy-sensitive resin layer.
An energy-sensitive resin layer may be formed by, for example, roll
coater application, spin coater application, spraying, dip coater
application, curtain flow coater application, wire bar coater
application, gravure coater application, air knife coater
application and cap coater application. Thus, an energy-sensitive
resin layer is applied on a surface where an irregularity is to be
formed.
The patterned mask or the direct drawing pattern has a regular or
irregular pattern consisting of an active energy ray blocking part
and an active energy ray transmitting part, and has a distance
between the active energy ray blocking part and the active energy
ray blocking part or between the active energy ray transmitting
part and the active energy ray transmitting part of preferably 1
.mu.m to 50 .mu.m, more preferably 5 .mu.m to 20 .mu.m.
There are no particular restrictions to a pattern shape; examples
generally include a circle, an ellipse, a ring, a polygon, a curve,
a straight line or a combination thereof. Examples of a light
source for an active energy ray include a carbon arc lamp, an
extra-high pressure mercury lamp, a high pressure mercury lamp, a
xenon lamp, a metal halide lamp, a fluorescence lamp, a tungsten
lamp and an excimer laser; preferably, a light source emitting a
light at a wavelength of 436 nm or less. A dose of the active
energy ray is preferably 0.01 J/cm.sup.2 to 1 J/cm.sup.2, more
preferably 0.01 J/cm.sup.2 to 0.5 J/cm.sup.2, particularly
preferably 0.05 J/cm.sup.2 to 0.1 J/cm.sup.2.
When the energy-sensitive resin layer is a negative type resin
layer, the layer is irradiated with an active energy ray using a
mask having a pattern consisting of an active energy ray blocking
part for an area where the energy-sensitive resin layer is to be
removed and an active energy ray transmitting part for the
remaining area, and then the energy-sensitive resin layer is
developed. Specifically, an unexposed part is removed completely or
to a desired depth by spraying an aqueous solution containing an
inorganic alkali or its salt such as sodium hydroxide, potassium
hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen
carbonate, potassium hydrogen carbonate and sodium meta-silicate;
or an organic base or its salt such as monoethanolamine,
diethanolamine, triethanolamine, tetramethylammonium hydroxide,
triethylamine and n-butylamine, or immersing in such an aqueous
solution.
If necessary, all parts in an energy-sensitive negative type resin
layer where an irregularity must be maintained are as a whole
heated or irradiated with an active energy ray, to correct or fix
the surface irregularity. Although there has been described an
example with a negative type energy-sensitive resin layer, a
composition of the energy-sensitive resin layer is not particularly
restricted, and thus may be of a negative or a positive type.
On an energy-sensitive resin layer, a surface irregularity can be
formed as described above, using, for example, a negative resist
from Hitachi Chemical Co., Ltd. (CR-700). When the energy-sensitive
resin layer is of a positive type represented by, for example, a
positive resist from JSR Corporation (PC403), the above pattern can
be inverted to form a similar surface irregularity.
Next, there will be described a process of forming a thin film
layer on a surface where an irregularity is to be formed and
pressing a transfer mold surface to the thin film layer as another
aspect of this example.
The irregularity formed as described above can be used to prepare a
transfer mold. Here, the mold has an inverse shape to the original
surface irregularity. A surface shape after transferring using the
transfer mold reflects the original surface shape, i.e., is
identical to the original shape.
Alternatively, the shape obtained by the above surface irregularity
forming process can be used as a direct transfer mold, whose
surface irregular shape is then used as a mold for forming a
transfer mold. Here, since transfer is conducted twice, the
transfer mold has the surface irregularity identical to that in the
original surface irregularity.
Alternatively, a thin film layer can be formed on a surface where
an irregularity is to be formed, and then a transfer mold surface
is pressed to the thin film layer for transferring, to form a
surface irregularity.
Although methods for transferring a surface irregularity will not
be specifically listed, such transfer can be also conducted by
depositing a thin film layer on a transfer mold and then
transferring the thin film to which a surface irregularity has been
transferred, besides the method involving pressing a transfer mold
to a thin film layer. Of course, transfer can be conducted by any
of those described in the above embodiments and other examples.
A transfer mold used may have a structure where a plurality of fine
surface concaves and convexes are formed in the whole surface or a
desired part of a substrate material surface such as a sheet, a
belt, a roll, a scroll or a partial curve of such a material. It
may be laminated on a pressure device or sandwiched between a
surface where a surface irregularity is to be formed and the
pressure device. During the pressing step, heat or a light may be
applied.
By seamlessly forming a belt, roll or scroll type transfer mold, a
surface irregularity may be easily made seamless. A surface
irregularity degree in the transfer mold should be generally
designed, taking into consideration deformation during curing a
transferred thin film layer. After curing, the thin film layer
preferably has the following dimensions: a difference between a
convex and a concave is 0.1 .mu.m to 15 .mu.m, particularly 0.1
.mu.m to 5 .mu.m; a convex pitch is 0.7 .mu.m to 150 .mu.m or a
pixel pitch whichever smaller both inclusive, particularly 2 .mu.m
to 150 .mu.m or a pixel pitch whichever smaller both inclusive.
FIG. 19 shows a cross-sectional view of a transfer mold used for
forming a surface irregularity and FIG. 21 is a cross-sectional
view of an example of a functional film, which is comprised of a
base film 521, an irregular film 522, a reflection film 523, a thin
film layer 524, a chemically stable thin film 525 and a core
526.
Although being not shown, a surface irregularity may be formed on a
metal belt surface, on which a film material may be applied to form
an irregularity.
FIG. 20 shows an apparatus for measuring reflection properties of a
diffuse reflection film. Assuming that an angle formed between a
reflected light 527 and an incident light 528 is .theta., a diffuse
reflection film exhibiting good reflection properties can be
obtained by increasing a brightness, i.e., a reflection intensity
observed in a normal line direction of the diffuse reflection film
within a required range of .theta.. For the required .theta. range
of -60.degree. to 60.degree., in a diffuse reflection film whose
surface irregularity is formed with the concave curve as shown in
FIG. 21, a diffuse reflection film exhibiting good reflection
properties can be obtained when a relationship between a height H
of the concave and the convex and the pitch P of the convex is near
a straight line represented by the equation P=7.times.H as shown in
FIG. 22.
For .theta. of -15.degree. to 15.degree., when it is near a
straight line represented by the equation P=30.times.H, a diffuse
reflection plate exhibiting good reflection properties can be
obtained. This means that when attempting to obtain diffuse
reflection to a normal line with a light source within a range of
60.degree. and further attempting to obtain further strong diffuse
reflection within a range of 15.degree., a shape combining the
range near the two straight lines represented by the equations
P=7.times.H and P=30.times.H may be acceptable. It is, of course,
not necessary that all of concaves and convexes are contained in
the above range near the two straight lines because a plurality of
shapes are inevitably formed in the process for manufacturing the
surface irregularity. Furthermore, influence of gap uniformity and
light interference in the liquid crystal layer must be taken into
consideration.
Therefore, assuming that a deformation rate in the thin film layer
is "a", an irregularity degree of the transfer mold surface is
preferably such that a height difference between a concave and a
convex in a convex surface is 0.1.times.a .mu.m to 15.times.a
.mu.m, particularly, 0.1.times.a .mu.m to 5.times.a .mu.m; a convex
pitch is 0.7 .mu.m to 150 .mu.m or a pixel pitch whichever smaller
both inclusive, further 2 .mu.m to 150 .mu.m or a pixel pitch
whichever smaller. The value of "a" depends on a material for the
thin film layer; for example, it may be 2, 1 or 0.7.
When the surface irregularity in the reflection film is formed by
the concave/convex complex curve as shown in FIG. 23, reflection
properties from a light source within 60.degree. to a normal line
are excellent in the case that a relationship between a height H of
the concave and the convex shown in FIG. 24 and a convex pitch P is
near a straight line represented by the equation P=3.5.times.H. It
is not necessary that the surface irregularity is arranged
periodically in plane, but it may be irregularly arranged.
In an LCD, moire may be generated when the period of the surface
irregularity is inconsistent with the pixel pitch. The period of
the irregularity is preferably equal to the pixel pitch or the
pitch divided by an integer, or alternatively the irregularity is
irregularly arranged. By arranging the irregularity in the transfer
mold surface, it can be used in an LCD without moire as long as
periodicity is deliberately provided.
There are no particular restrictions to the surface shape of the
irregularity, but preferably selected from, besides a complex
plane, a concave surface, a convex surface, a concave-convex
complex surface, a concave or convex surface approximate to a
sphere or paraboloid and a concave-convex surface, because by using
a curved surface, a diffused light may be obtained from a light
source position within a wider range.
In particular, for a diffuse reflection film for a semi-transparent
and semi-reflective type LCD, a smaller average height difference H
is preferable in the light of a cell gap and .DELTA.nd (refractive
index (thickness) because a light diffusing surface must be formed
within the LCD cell. However, since a convex pitch P cannot be so
reduced to generate optical interference, the lower limit of an
average height difference H is determined from the above equation
for P and H. Hereinafter, .theta. is an absolute value for better
understanding.
A refractive index "n" of an LCD cell depends on its structure; for
example, a diffusion direction E required when n=1.3 is a range of
less than 50.3.degree.. With a diffusion direction of 50.3.degree.
or more, total reflection occurs in an interface between the LCD
cell and the air. Therefore, it is necessary to reduce a reflection
intensity R in a diffusion direction of 50.3.degree. or more while
increasing a reflection intensity R of less than 50.3.degree.. For
example, a diffusion direction .theta. required when n=1.5 is a
range of less than 41.8.degree.. In a diffusion direction of
41.8.degree. or more, total reflection occurs in an interface
between the LCD cell and the air. Therefore, it is necessary to
reduce a reflection intensity R in a diffusion direction of
41.8.degree. or more while increasing a reflection intensity R of
less than 41.8.degree..
In general, a viewer watches an LCD at the front. Here, incident
light is less from the direction of the eye to the LCD while being
more from a direction of 10.degree. or more from the eye to the
LCD. For example, when n=1.5, incident light from the air at
22.8.degree. becomes a light of 15.degree. after passing through an
interface between the LCD cell and the air. Therefore, it is
necessary to particularly increase a reflection intensity R near a
direction of .theta.=15.degree. of the diffuse reflection film
formed within the LCD cell.
For example, when n=1.3, incident light from the air at
19.7.degree. becomes a light of 15.degree. after passing through an
interface between the LCD cell and the air. Therefore, it is
necessary to particularly increase a reflection intensity R near a
direction of .theta.=15.degree. of the diffuse reflection film
formed within the LCD cell. For manufacturing a light diffusion
surface used for a diffuse reflection film for a reflection type
LCD, it is necessary to design an average height difference H and a
pitch P by producing an equation in the light of the above
reflection intensity properties.
A transfer mold can be manufactured by pressing a direct transfer
mold to a deformable supporting film. A temporary supporting film
can be a supporting film formed by the steps of forming a
deformable undercoating layer, to which a direct transfer mold is
pressed and curing, if necessary, the undercoating layer. During
the step of pressing, heat or a light may be applied.
When forming a thin-film flat light emitting device or liquid
crystal device such as an organic EL device and an inorganic EL
device on a reflection film, the surface of the reflection film
must be flat.
As described above, for the purpose of this, a reflection film
comprising a surface irregularity can be deposited on a substrate
consisting of a base film or functional film and then a flattening
film can be laminated.
This example will be described with reference to FIG. 25. A surface
irregularity is formed on a substrate consisting of a base film or
a functional film as described above. The surface irregularity may
be formed by forming an energy-sensitive resin layer on a surface
in the above substrate where the irregularity to be formed,
irradiating the energy-sensitive resin layer with an active energy
ray via a patterned mask or by a direct drawing method and then
removing the exposed part or the unexposed part in the resin layer
by a developing solution; by forming a thin film layer on the
surface in which the irregularity to be formed and pressing a
surface of a transfer mold onto the thin film layer for
transferring; or alternatively, by depositing a thin film layer on
a transfer mold and then transferring the thin film layer to a
surface where the irregularity is to be formed. Then, a reflection
film is formed, which can be also formed as described above without
any problems.
Finally, a flattening film is deposited on the reflection film. The
flattening film can be deposited by, for example, application,
lamination or transfer. This figure shows examples of both
lamination and transfer.
It is necessary that a surface in the flattening film to be in
contact with the surface irregularity is deformed along with the
shape of the surface irregularity, while the opposite side to the
surface to be in contact with the surface irregularity is flat.
There are no particular restrictions to its material as long as the
above function can be achieved; thus, for example, an organic resin
can be used.
A reflection film may be formed by preliminarily forming a
reflection thin film on a surface irregularity in a transfer mold,
depositing a thin film layer and then transferring the thin film
layer to a surface in which an irregularity is to be formed.
A flattened layer consisting of a reflection film and an
undercoating layer may be formed by preliminarily forming a
reflection thin film on a surface irregularity in a transfer mold
comprising an undercoating layer, depositing a thin film layer and
transferring the thin film layer to a surface in which an
irregularity is to be formed.
The undercoating layer may be made of, for example, at least one
organic polymer selected from polyolefins such as polyethylene and
polypropylene; ethylene copolymers such as those of ethylene and
vinyl acetate, ethylene and an acrylate, ethylene and vinyl
alcohol; polyvinyl chloride; copolymers of vinyl chloride and vinyl
acetate; copolymers of vinyl chloride and vinyl alcohol;
polyvinylidene chloride; polystyrene; styrene copolymers such as
those of styrene and (meth)acrylate; polyvinyl toluene; vinyl
toluene copolymers such as those of vinyl toluene and
(meth)acrylate; poly(meth)acrylate; (meth)acrylate copolymers such
as those of butyl(meth)acrylate and vinyl acetate; cellulose
derivatives such as cellulose acetate, nitrocellulose and
cellophane; polyamides; polystyrene; polycarbonates; polyimides;
polyesters; synthetic rubbers; and cellulose derivatives.
If necessary, for curing the film after forming the surface
irregularity, an additive such as a photoinitiator and a monomer
having an ethylenic double bond may be preliminarily added.
Alternatively, photosensitivity of the material may be negative or
positive.
A temporary supporting film used in this invention may be made of a
chemically and thermally stable material which can be formed into a
sheet or plate. Examples include polyolefins such as polyethylene
and polypropylene; polyhalogenated vinyls such as polyvinyl
chloride and polyvinylidene chloride; cellulose derivatives such as
cellulose acetate, nitrocellulose and cellophane; polyamides;
polystyrene; polycarbonates; polyimides; polyesters; and metals
such as aluminum and copper. Among these, particularly preferred is
a biaxially stretched polyethylene terephthalate which is
dimensionally stable.
Although a thin film layer may be made of, for example, a
composition comprising a deformable organic polymer, an inorganic
compound or a metal, preferably an organic polymer composition
which can be applied on a film and wound-up as a film is used.
Furthermore, if necessary, to the material, additives such as dyes,
organic pigments, inorganic pigments, powders and their composites
may be added alone or in combination.
The thin film layer may be made of a photosensitive resin
composition or a thermosetting resin composition. There are no
particular restrictions to a dielectric constant, a hardness, a
refractive index and a spectral transmittance of the thin film
layer.
Among these, preferred are those exhibiting good adhesiveness to a
film and good peelability from a film. Examples of a material which
can be used include polyolefins such as acrylic resins,
polyethylene and polypropylene; polyhalogenated vinyls such as
polyvinyl chloride and polyvinylidene chloride; cellulose
derivatives such as cellulose acetate, nitrocellulose and
cellophane; polyamides; polystyrenes; polycarbonates; polyimides;
and polyesters. Alternatively, those exhibiting photosensitivity
may be used. Optionally, a photosensitive resin which can be
developed by, for example, an alkali, can be used for removing an
unnecessary part while leaving a part where the surface
irregularity must be present. For improving heat resistance,
solvent resistance and shape stability, a resin composition curable
by heat or a light after forming the surface irregularity may be
used. Furthermore, an additive such as a coupling agent and an
adhesiveness-endowing agent may be added to improve adhesiveness to
a film. For improving adhesiveness, an adhesiveness-endowing agent
may be applied to an adhering surface in a film or thin film
layer.
A resin which can be developed by an alkali is preferably selected
from those having an acid number of 20 to 300 and a weight average
molecular weight of 1,500 to 200,000; preferable examples include
copolymers of a styrene monomer and maleic acid or their
derivatives (hereinafter, referred to as an "SM polymer"), and
copolymers of a carboxyl-containing unsaturated monomer such as
acrylic acid and methacrylic acid with a monomer such as styrene
monomers, alkyl methacrylates (e.g., methyl methacrylate, t-butyl
methacrylate and hydroxyethyl methacrylate) and alkyl acrylates
having a similar alkyl group.
Examples of an SM copolymer include those prepared by
copolymerizing a styrene or its derivative (styrene monomer) such
as styrene, (-methylstyrene, m- or p-methoxy styrene,
p-methylstyrene, p-hydroxystyrene and
3-hydroxymethyl-4-hydroxy-styrene with a maleic acid derivative
such as maleic anhydride, maleic acid, monomethyl maleate,
monoethyl maleate, mono-n-propyl maleate, mono-iso-propyl maleate,
n-butyl maleate, mono-iso-butyl maleate and mono-tert-butyl maleate
(hereinafter, referred to as "copolymer (I)"). Copolymer (I) may
include a copolymer (I) modified by a compound having a reactive
double bond such as an alkyl methacrylate (e.g., methyl
methacrylate and t-butyl methacrylate) (copolymer (II)).
The above copolymer (II) can be prepared by reacting an acid
anhydride or carboxyl group in copolymer (I) with an unsaturated
alcohol such as allyl alcohol, 2-butan-1,2-ol, furfuryl alcohol,
oleyl alcohol, cinnamyl alcohol, 2-hydroxyethyl acrylate,
hydroxyethyl methacrylate and N-methylolacrylamide and an epoxy
compound having one oxirane ring and one reactive double bond such
as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether,
(-ethylglycidyl acrylate and monoalkyl-monoglycidyl itaconate.
Here, it is necessary that a carbonyl group required for alkali
development remains in the copolymer. In the light of
photosensitivity, it is also preferable to endow a polymer other
than an SM polymer which has a carboxyl group, with a reactive
double bond as described above.
By forming a thin film layer and/or an undercoating layer to a film
thickness larger than a height difference in a transfer mold having
a surface irregularity, the surface irregularity can be readily
reproduced. If the film thickness is equal or smaller than the
difference, a surface irregularity may be deformed, and
furthermore, during forming a surface irregularity, a thin film
layer is broken in a convex in the transferred surface
irregularity, leading to formation of a flat part which may result
in insufficiently efficient reflection properties.
The thin film layer and the undercoating layer may be formed by,
for example, roll coating, spin coating, spraying, wheeler coating,
dip coating, curtain flow coating, wire bar coating, gravure
coating, air knife coating or cap coating.
When a surface irregularity is transferred using a negative type
photosensitive resin as the thin film layer, its shape stability is
ensured by curing its photosetting part by exposure using a
light-emitting apparatus. Examples of an applicable light-emitting
apparatus include a carbon arc light, an extra-high pressure
mercury lamp, a high-pressure mercury-vapor lamp, a xenon lamp, a
metal halide lamp, a fluorescence lamp, a tungsten lamp and an
excimer laser. The light-emitting apparatus may be selected from
those for forming a pattern such as pixels and BM, as long as it
can cure a preformed irregularity. Thus, an apparatus which can
emit a light quantity equal to or more than the quantity which can
initiate a photosensitive resin. Therefore, a UV-irradiating
apparatus using a scattered light can be used, which can be
incorporated in a line generally used as a substrate washing
machine. Such a machine can be used to form the film with a lower
cost and a larger allowance in an exposure in comparison with a
procedure using a photomask. Although a material whose
photosensitivity is negative has been used above, it may be of a
positive type.
Exposure is conducted before or after peeling off the transfer
mold. Furthermore, if necessary, the irregularity may be cured by
heating preferably at 50 to 250.degree. C. Heating is conducted
after peeling off the transfer mold.
FIG. 26 shows a liquid crystal structure having the reflection
electrode with an irregular shape described in Example 10.
In FIG. 26, a reflection electrode is formed on a base film in an
irregular shape. In this figure, on a base film 414 is transferred
an irregular film 414a, on whose surface is then formed a
reflection electrode 413 and a transparent electrode is formed on a
flattening film 414b for flattening.
An organic EL device has a structure shown in FIG. 7C. Although
being not shown, it may have the same liquid crystal structure as
that in the prior art. For the purpose of this invention, it can,
of course, have a variety of structures.
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